Not every prototype needs a case but sometimes its nice to have some protection for the bottom of the board.

I usually just use a scrap of wood. Leftover laminate flooring makes a great base.

When the project needs a little more class like my Cypress developer board, I 3D print a coaster.

I used SCAD to make a simple coaster with posts to match the board holes.

It takes about a half hour for a small one so its reserved for special projects.

You can use tin nuts or simply melt the posts to hold the board in place.

The files can be found here:

Generic PC Board Coaster