Prefolds are the hardest thing you will ever make, seriously... Two pieces of absorbent fabric, sandwiched together and stitched around the edges... You will have no probs making your own.
You can add an extra layer down the centre third, but they are easy. They are smaller than flats, which saves on bulk.
I had 2 terry flats and found them much too bulky and large on DD - she was very lean and very long, and they were a PITA, so we used flanny ones. They dried in about 2 hours in the sun on a bad day and 15 mins inside in the Perth summer lol

Covers... Maz are good, I used Tots Bots (not sure what they do now, but they used to have fleece and PUL covers, I used both. They had extra leg gussets (the PUL ones) so excellent for containment. I *think* they may have gone back to this design after changing it a couple years ago (morons lol)
I have here to use this time a Bummis cover as well which looks good, also has the extra leg gussets but appears to be wool I think?

You will only need 6 covers I would think - they dry very quick and you don't wash them every wet nappy, I used to hang them over the side of the change table and air them, use them every second wet change, and pop them in the wash when soiled or after 2-3 uses.

You can also use AI2 shells like covers - like small IB's or even your OSFM pockets.