There are as many ways to install and mount a DSD Button Device as there are sim racing enthusiasts. We recommend mounting solutions from Ram Mount or Arkon Mounts. Both manufacture various mounts, clamps, holders and other components to fasten in place securely thousands of types of things.
We also know that every sim racer has his or her own needs and knows those needs the best. That said, beyond making the suggestion to see Ram or Arkon, we don't offer more for mounting ideas.
Download Ram Mount Guide Here - DSD Official Mounting Guide
Ram Mount Website
Arkon Mount Website
USE SAE #12 or SAE#10 coarse threaded screws to attach your mount to your DSD Device. Lengths of ~3/4"/19mm generally work.