I had a high-quality lens rescued from a piece of militaria and decided to make a stand for it. A piece of clear plastic tube had a recess cut into it to accept the lens and hold it exactly at the lens focal length above whatever the tube was placed upon. Another piece of tube was reduced in diameter to be a interference fit in this recess. It serves to hold the lens in place without the need for any glue. On the top of this latter piece a circle of 0.010" thick clear sheet plastic is lightly glued. It keeps dust off the lens and acts as a sacrificial protection for the lens. Looking closely at the second picture you can see there's already a break in it, the result of a dropped tool.
This arrangement is very convenient. To read a scale or vernier, you simply set the plastic tube on it and the lens is automatically focused on what you want to magnify.