When it comes to LEGO stop-motion sets, keeping them firmly attached to your table or desktop is a must. Some folks use tape or blue tack, but I like the versatility that clamps provide. I started with regular spring clamps (like these) from a hardware store, before Sean Kenney introduced me to the Mini Quick Grip clamps made by Irwin.
Despite being the 6″ size, the clamps I have here actually open up to about 6 3/4″. This extra space can useful if the floor of your set is more than a few bricks high, or if you need to support a large backdrop. The trigger-looking handle allows you to adjust the amount of pressure you’re applying, and the rubber pads prevent damage to your precious LEGO baseplates (in fact, I usually end up with stud impressions in the pads after removing them).
If you’re looking for a way to solidify your set and tabletop without harming your LEGO, I highly recommend giving these clamps a try. They’re a bit on the pricier side ($13 at Home Depot, or $20 for a 2-pack), but well worth it.