Looks like a foldable topper?
If so, I would:
1. Cut a piece of 1/4" ply the exact size/shape of the topper (including the seam cut.)
2. Glue and staple it to the bottom of the topper (covering the chip wells)
3. Flip it over and fill in the wells with the appropriate thickness wood to be flush with the felt.
4. Spray super 77 spray on existing felt, wait until tacky. Recover with SSC, wrapping around the edges and stapling to the bottom.
I would want to add padding, but not sure how it would stand up to folding. If you are ok with not folding for storage, just add the 1/4" ply to the top, then glue on some volara for the playing surface pad, then add the SSC.