This standing desk was built by propping up a hollow core door on four stacks of bricks. The plan was to add 15 inches of height because I measured a 15 inch difference between the height of my shoulders when I was a sitting and standing position.
The biomechanics are a bit different, so I might have added another inch or two in height. At some point I might try shimming it up by adding some more bricks, boards or tiles. When I first started using it my hands felt uncomfortable using the mouse on the desk surface, so I set up some books as a platform for mousing. After a few days it seemed that my body adapted to the new position and I use the mouse without the platform.