The easiest way to build a training table is from one sheet of plywood 4' x 8' x 1/2 or 3/4 inches.
Cut the sheet in half the long way.
Cut one of the halves in half the short way.
This gives a total of 3 pieces: one 2' x 8', two 2' x 4'.
Fasten one of the 2' x 4' pieces to each end of the 2' x 8' piece with hinges so they can serve as ramps and be folded flat over it for storage.
Nail some strips across each of the ramps for traction.
Attach 2' tall legs under the main table and some bracing for stability. The legs can be made to fold to provide easy storage and hauling.