Purdue University’s Mechanical Engineering Machine Shop has plans and instructions for building a machinist clamp. The drawings are in PDF files and the instructions are in a Microsoft Word Document. If you don’t own a copy of Word then you may need this free Word Viewer.
The instructions are pretty detailed and even tell you what speeds to use. But they assume you are using their machines, which are obviously equipped with DROs.
They also have plans for a pen holder and picture frame.