MDF-foam-MDF is not going to give you constrained layer damping, and MDF is a bad choice for audio in general, IMO. But there are good materials for sale at Home Depot. See if they have a cement paver that is large enough to support your TT, for one example. Check out Adona; they may sell their excellent CLD shelves separately. Or used.
I would use lead shot, not rice, if not sand, as a filler in your Lovan.
I would use lead shot, not rice, if not sand, as a filler in your Lovan.