sorry for the upside down pic but you get the idea. don't nail it together. use screws. pad the sh!t out of it and don't leave sharp or hard corners that will become a presurre point in the padding. those will dent foam. make them roughly 45" tall with a 10" - 12" pocket, but it depends on how tall you are. setup lights about 6" - 8" taller then your racks.
racks are #1 thing to start with. and easy. get lighting though. so cheap and so much better to shape with.