This is probably a case of grannies sucking eggs...
but.
Once you've worked out where they all go; Do as I was taught by the guy who mentored me through my first bike build.
Get a a couple of thick bits of card, draw out the shapes of your timing cover and primary chaincase, mark the position of the holes and poke through them with a screwdriver.
Every time you have those cases off the bike, put the screws in the relevant hole in the cardboard. Makes reassembly nice and easy.
Cheers,
Iain