If you don't want anything fancy, just a wooden plaque, look up your local trophy shops which sells finished plaques. Clear acrylic discs are commonly used for anime kits. I'm selling my surplus of wooden plaques ( the 3 wooden plaques on the top left corner) and acrylic discs (the 3 bottom right). There some very beautiful acrylic blocks they use for showrooms available from potomacdisplay.com, but they're very expensive.
Here I'm drilling one of the 3 holes which pins Misato to the 4" acrylic base. You really want to have at least two pins for balance, but 3 pins will guarentee your figure will never fall. Originally I wanted to use epoxy glue on her soles to affix her to the base, which is why I scratched off the paint on her sole. However if your figure is pinned, superglue is very strong if you apply it to the pin - the pin will break before it's being pulled out of the hole! So epoxy wasn't necessary.