I cut 48x96 sheets into 48x32 benchtops, I find that ideal. Deep enough to hold a lot but shallow enough to still reach the shelves.
Use Gorilla glue to laminate a piece of thin (1/4" or 3/8") ply to a piece of rigid pink foam board, with another piece of thin ply on the bottom. This foam-core sandwich is stiff but lightweight, acoustically dead, and very cheap. You can use a ton of random objects or just a vacuum-bag to apply the lamination pressure. Stick some one-by on the edge and radius it with a router, and you're done.
Use Gorilla glue to laminate a piece of thin (1/4" or 3/8") ply to a piece of rigid pink foam board, with another piece of thin ply on the bottom. This foam-core sandwich is stiff but lightweight, acoustically dead, and very cheap. You can use a ton of random objects or just a vacuum-bag to apply the lamination pressure. Stick some one-by on the edge and radius it with a router, and you're done.