u/An0n-xm

There are a dozen verses that directly refer to the earth as being flat or flatlike. Here are 2 of the most explicit verses:

"And at the Earth, how it has been flattened?" (Quran 88:20)

"And after that He spread the earth" (Quran 79:30)

The tafsir also explicitly support this in a number of places.

Tafsir Al-Jalalayn states "{after that He spread out the earth}, He made it flat for it had been created before the heaven but without having been spread out".

In another place, Al-Jalalayn says: "As for His words sutihat (88:20) ‘laid out flat’ this on a literal reading suggests that the earth is flat which is the opinion of the scholars of the revealed Law and not a sphere as astronomers ahl al-hay’a have it even if this latter does not contradict any of the pillars of the Law."

Tafsir Ibn Samin Al Halabi says "The Almighty’s saying: {And the earth, how it has been flattened} it means it expanded and widened as his saying {And after that He spread the earth} I.e, it was spread after it was a ball"

Tafsir Al Qunawi says: “Although the author’s claim (that the Earth is round) is well meant, the claim that it is flat is more likely to be correct because it was the opinion of Ibn Abbas and Ibn Umar (may Allah be pleased with them) and the apparent interpretation of the verses {and the earth we have spread it} and {You will not see therein a depression or an elevation} and {And after that He spread the earth} indicate that it is flat. And Ibn Abbas and a multitude of scholars are more knowledgeable of the Arabic tongue and its subtleties, so it is no crime to lean towards the opinion of those who have understanding. And the claim of sphericity is that of the philosophers, and apparently the author (Al-Bayadi) it is following opinion of Imam al-Razi and is based on the rationalist arguments for sphericity in his tafsir. The author believes that claim and while there is nothing wrong with that it is safer to follow the opinion of the salaf.”

Ibn Abbas said in a lengthy narration in Tafsir Abdurazzaq: "He then created Nun (whale), then the earth was spread over it. When Nun stirred, the earth shook. He created the mountains to secure it, for indeed, they prevail over the earth."

Again, there are more verses and many more scholars like Tabari, Ibn Mujahid, Suddi, Thalabi, Ibn Attiyah, Shawkani, Qurtubi, and on and on who directly and/or indirectly affirm a flat earth per islamic texts.

The hadith also reinforce this view. This hadith mentions hellfire's gates blasting open when the sun is at its zenith. The problem is, the sun is always at its zenith somewhere on earth, meaning hellfire's gates are always blasting open. But why would the Prophet say this as if it's something that happens only once in the day at the zenith? Well, this only makes sense on the flat earth model:

https://sunnah.com/ibnmajah:1252

Another hadith expresses a similar concept, the shaytan is accompanying the sun and then departing from it 3 times a day (at sunrise, zenith and sunset). Again, this only makes sense on a flat earth because on a round earth, this shaytan would be always stuck to the sun because it's always rising, at it's zenith or setting somewhere on earth:

https://sunnah.com/ibnmajah:1253

And then there's the infamous hadith about Allah descending to the lowest heaven in the last 3rd of the night. Again, it's always the last 3rd of the night somewhere on earth so that means Allah should be perpetually stuck in the lowest heaven. In order for this hadith to make sense, we would have to accept the flat earth model:

https://sunnah.com/bukhari:6321

Now a number of scholars came to the realization that the earth is spherical after they were exposed to the works of Greek disbelieving scholars, which came about 300 years after Muhammad's death. Makes one wonder, why did it take Muslims receiving knowledge about this basic fact of reality from disbelievers instead of the creator of the universe? Why was it so hard for Allah to express himself clearly about the shape of the earth? When Islamic scholars started to shift their understanding, they started to cling onto one measly verse:

"He created the heavens and the earth for a purpose. He wraps the night around the day, and wraps the day around the night. And He has subjected the sun and the moon, each orbiting for an appointed term. He is truly the Almighty, Most Forgiving." (Quran 39:5)

The word used here is yukawwir which means to wrap (usually over a round object), which suggests it is wrapping over a round earth. However, this can he debunked in a few ways.

1. The verse doesn't mention the earth anywhere, it only says the night is wrapped around the day and vice versa. It's simply describing the cyclical pattern within the 24 hours of a day. Other verses describe this same changing of the guard between night and day like in (39:5), (22:61), (31:29), (35:13), (7:54), (13:3) so this verse simply falls in line with them.
2. Even if one were to be generous, this could be interpreted as the night or day wrapping over the physical dome (sky/heaven) supported by invisible pillars over the flat earth. The Quran often describes the sky as a protective ceiling/canopy/roof and many scholars like Iyas ibn Muawiyah, Hasan al Basri, Qatadah and others interpreted this as a physical dome.
3. If you take this verse literally to describe a round earth then you are suggesting the night and day are physical entities that physically wrap/merge/enter each other. As a result, they are akin to physical veils of darkness and light. Now this is opening a can of worms. A figurative interpretation is a safer bet as it uses the action of wraping/merging/entering in a metaphorical way that protects it from this criticism. Unfortunately, Muslims can no longer use this as proof of a round earth since it's now understood figuratively.