Thanks to LoserKid418 for adding access to the OnShape object for his original design!
I'm in the process of learning Fusion 360, so I used his original object as a reference to remake it in F360. This is the first thing I've created in F360, so I'm sure there are things I could do better... but it works great and you can edit the F360 sketches to change the length and width of the wrench holder as well as the slot widths and spacing between wrenches. The F360 file for the template object is included with the thing files.
I've included some versions that I created for wrench sets that I have (some aren't really sets, they're just somewhat random collections of tools I've put together over the years).