Is there a way to avoid the ugly gap while using the right (or left) slant hash stroke type?
My workaround is to create a circle-like shape instead of circle:
…and to adjust the two ends manually:
It looks ok, but it's not really a solution.
I am not entirely sure about this but I'll suggest an alternative if you'll hear me out.
You could create a a elliptical object, use the type on path tool, and type out a bunch of common slashes (or back slashes depending on what you want) and set the paragraph to fully justified. Add more slashes to make it tighter, or remove some to make the pattern looser and play with the point size to achieve the desired result.
I'm interested to see what others suggest to do in order to achieve the result you're looking for.