Apologies if this isn't the right forum. I play 40K and this is a project so I figured this was one of the better places.

So I've been watching YouTube videos and other random stuff online that has me wanting to build a small gaming table for playing at home. I'm pretty much set on just about all the aspects about it. I'm planning on building it with a plywood board and reinforce the underside. However I want to put polystyrene sheets (I think?) on the top layer for the actual models.

Therein lies my question. What kind/size of polystyrene should I look to get? About how thick? 1/4"? 3/8"? Honestly I'm not sure what sizes they come in. A second question, where is the best place to get it? I had been defaulting to maybe going to Michaels/Hobby Lobby but was thinking it might be cheaper at a hardware store (and also in bigger sizes).

So...does anybody have any suggestions? I assume it doesn't make sense to mail off for it either. I guess I don't mind using a bunch of smaller ones and attaching them to the plywood but I'd rather stick to larger sheets for sake of ease.