just buy 18mm ply and chop it up to the depth u want...
no real plans just get as much mileage out of the ply as poss.....
I work it so the off cuts make the shelev's or the ends.....
prefer never to make em longer than around 6' to get the off cuts.....they get to heavy to fit alone.....
all mine get the 18mm fot the top, bott and the ends plus at least one of the dividers......
the back is usually 1/2" all glued n screw'd.....
for dodgy walls I tend to use a French cleat....make fitting easyer and u can get the mounts in whereever poss....
been known to use studding and epoxy for mounting the cleat rail.....
Do u know why they call it a French Cleat......
thats because when they do a runner for not paying the rent they can remove fitting in 2 mins....hahaha...
How very true....