Customizable thing with four columns located at the corners of a rectangle and mounted on a base. You can specify the location of the columns, the size of the base, etc.
The default data in the Customizer file creates a 120 x 80 mm base for a Raspberry Pi 2 Model B board. The 2.5 mm mounting holes for the board work well with #4 sheetmetal screws. Adjust the hole size so that the screws you will be using self-tap by cutting their own threads in the column hole. (You may need to experiment a bit; the exact size seems to depend on the printer you are using and the type of plastic you are extruding.)
If you want more post options, or a more complicated arrangement of posts, see my "Polygon Columns with Holes and a Twist" Thing (http://www.thingiverse.com/thing:1370889) which features individual positioning of up to 10 columns (and has uses a lot more parameters).