maple has some good quality’s depends on what your trying to get out of your system.
I found maple a little too soft for my tastes I prefer higher mass like granite I find it more detailed then maple. either way, yeah works well. oh bamboo is very good alternative as well if not a bit more expensive to layer it.
Any competent wood worker can build you some shelves at any dimensions you need. If you go stone instead any stone counter top cutter in your city will be able to make it for you or a tombstone cutter may have some leftovers (that’s where I got mine).
I have a 3"x26"x20" granite block I use at 165lbs plenty of mass.
I’ve been thinking of trying a sandwich of stone and wood as a project with some green goo or similar in between, (used between acoustic isolation panels like 2 sheets of drywall to form a sound barrier between condo units for example).
note; I tried isolation via vibropods etc as well as pin points I would recommend you try isolation and direct coupling (pin points). different sound for both ways neither better then the other just different. You should listen to both to make a decision on what you like in your system.
for me I found coupling and mass to give the best sound in my system. I found isolation muddied up the sound a little to much but did add a quieter background. its a trade off either way that’s why I suggest trying both on the cheep and then make something-buy something nice.