After looking at other dry erase marker holders, many of which store them standing with cap up (which dries out the markers faster), I decided to make a holder that can be mounted to the whiteboard with magnets (glued to the back) that holds the markers face down. The top slides onto the bottom.
Currently the file uploaded holds 6 markers. I will be making one that can hold 4 soon, and will add it to the file list.
I am also currently working on a bug that showed itself after uploading this, and will be fixing it shortly.