Some, if they're light enough, will hang off a screw or dowel by one of the bolt or indicator pin holes. Otherwise they get laid flat (I have a shelf just for gaskets). I have some antique head gaskets that I set up a gig to hang them on, supporting their weight over a few holes, that are good as new - after 20 years.
Ones that have been warped (what I do, sometimes that's the best you can find), I fabbed a "press" (one side milled and sanded wood, the other an old marble countertop chunk) to re-flatten them, and a similar gig (more countertop marble and sheets of those thin cigar box cedar liner sheets) to store them to prevent them from re-warping until used. I've saved one-off gaskets with folds and wrinkles that should have been the end of them this way...