u/Ok-Incident-5236

First sff pc build and scratching my head…
Not sure I am being a complete moron but the online manual is making 0 sense to me,
I want to setup in the 2.75slot configuration am I meant to be putting a spacer in this gap? (1st image)
In regards to the pcie adapter I need the 35mm of spacing but then do I need to use a space to get it to sit square against the rear of the frame?
If so it then seems like the countersink screws are too long and leaves me with 1-1.5m of play?
Am I right in thinking that this also means I just turn the case upside down once fully built for the fans to be on top as exhaust or again am I being a moron? Any and all help is very much appreciated

New build bought just over 18 months ago, surprise surprise came with no turf or garden of any sort just mud and rock.
Have spent the last 6days pulling out rocks the size of a child’s torso. Levelling and seeding.
Hoping I’ve got this in before the cold sets in and makes all my effort meaningless.
Have I missed anything? Does it look good?
Excuse the 7ft barrier. We have a dog that can vertical jump a 5ft fence which we found out shortly after putting the first layer up…