I've had folks ask what I do with bases. If they are on a paved area, I usually just color the base that way and leave it. The pit area is a good place for this as it allows me to move folks around for maintenance, cleaning, boredom, etc.
I've also done what Harry has shown using a clear base - I have many more to do that with too and that would work great for the pit areas.
For the folks in the infield though, I've always taken the bases off and simply glued them in place with Modge Podge matte glue. Easy to remove or re-fix if they get hit - but the PDR safety crew is usually pretty good keeping folks out of dangerous areas. Usually...
To take the bases off any figure - plastic, resin, or 3d - I use my trusty Ryobi belt sander. You have to be careful not to get a sanding burn, but you can easily remove bases in just a few seconds per figure. I simply crank it up, carefully hold the figure to the belt, and check it to ensure I'm not getting too much material off.
A few minutes later - voila!