What is a good base for speakers

Fussing with setting up a new system in basement. My vintage ADS L710's sit on original stands that don't have fittings for spikes. As the stands sit on a carpeted floor, they rock a lot (no pun intended). I'm thinking of some sort of base to settle them down. Looking for suggestions of a material appropriate for stability  - any experience with wood butcher block, granite or slate cutting boards as a base? More DIY than expensive. Thanks for any suggestions.