This is a great “Sub-dude” DIY project that practically anyone can do for about $15-25. Use 1/2" MDF for the base which is cut to the size of your sub, wrap it in felt material you can buy from a fabrics store, and place it on something that is not wooden or stiff, i.e. rigid foam, cork material or durable rubber. The "feet" should be about 2" off the floor.
Essentially you are creating a de-coupler to REDUCE, not eliminate bass transference to the floor. Especially wooden floors. Mine looks very nice and I think the bass response is better - tighter. I could care less what my downstairs neighbors think about the sound. The blast their must enough as it is.