u/greenwavetumbleweeds

I've never made soap before, brand new beginner here. My goal is to have liquid soap at the end that's moisturizing. It's just for me, and I don't care how it looks or if I have to shake it or it only lasts a month (etc).

I have a recipe for bar soap that sounds really easy and simple to me, just kefir and lye and other things I already have on hand. (The lye does not sound simple in that it's dangerous.)

I then have a recipe for liquid soap (hand) that's about converting bar to liquid soaps. It involves a hard bar of soap, then some water, oil, glycerin maybe. It has me using a food processor on the bar of soap, then melting it down.

Overall then, my question is this: do I still need to cold proof it? Doesn't seem like a big deal to do it, but also seems weird to spend all that time making a hard bar just to melt it down again.

Somewhat of a beginner, but my searches have me progressively confused. I have a "normal" sewing machine.

I want to make an undershirt (but not super lightweight) merino shirt, toddler sized. I want a closed seam for comfort. I thought of French or Felled, but believe I need a zig zag variation to account for the stretch? I've used French anyway on a stretchy thin fabric, but it was super thin. The shirt fabric would be thicker.

I've only ever used a French seam, with a zig zag stitch. I found a flatlock lookalike tutorial (allegedly great for stretch), but it has exposed edges on the sides (not comfy). Can I really not just do a flat felled seam with zig zags, or a flatlock like lookalike then fold one over and stitch with a zig zag?

What type of stitch is best for this? Looking for comfort and durability. I don't care how it looks that much.