I use this gasket material:
https://www.parts-express.com/Speaker-Gasketing-Tape-1-8-x-1-2-x-50-ft.-Roll-260-542However; no gasket material can effectively isolate the driver from the baffle if the driver is attached with screws which transmit the vibration.
To maximally isolate the driver from the baffle, you can just glue it on with silicone.
1) Set the driver 3/8" away from the baffle board using small spacers.
2) Fill the gap with RTV silicone and let is set up.
3) Remove the spacers and fill the gaps where the spacers were with RTV silicone, to complete the seal.
Now there are no hard connections to transmit the driver's vibrations into the baffle-- only the soft, dampening silicone.
The downside is that you would have to cut thru the silicone if ever wanted to replace the woofer.