My DIY standing desk is an 18" wooden coffee table with a plastic storage container, the box my speakers came in, and the box my external monitor came in. The storage container and one of the boxes act as a pedestal for my laptop (which I removed the broken screen from a few months ago) and my speakers and the other box hold up the external monitor. A spare t-shirt is placed under the front or back of the base of the monitor depending on whether I want it tilted up or down, and to what degree.
It's hardly stylish but functionally I couldn't ask for more.
Standing is nice precisely because it's slightly uncomfortable to do for longer periods of time. It forces you to stretch, move around, and take periodic breaks from staring into the screen.