Andrew Looney proposed affixing foam "feet" at the corners on his blog, Wunderland. Fan Daniel Hess (of Midsouth Makers) created a 3D-printable pegboard tray to serve the same purpose: lifting the board from the table so the pegs can fully seat.
When I received my demo copy today, I hacked together the following solution, using only cellotape and one of the punchout frames from the included board tiles. The results are sturdy, snazzy (if I may say so myself), and in keeping with the aesthetic of the components (since they use identical material).
* your very own copy of Fluxx: the Board Game, complete with
* at least one of the punchout frames; and
* a utility knife, with, of course,
* a good cutting surface; and don't forget
* the cellotape.