Yes — placing the CPL behind the square ND filter, closer to the lens, is normal for holder systems like Lee-type designs and generally causes no issue.

If you’re asking about ideal optical order, the ND filter would theoretically be better closer to the camera because some materials can show slight birefringence, which could interact with polarized light. In practice, though, this is mostly a theoretical concern with good-quality filters. It’s more likely to matter with stressed glass or plastic filters, not typical quality ND filters.

So for a standard holder setup, using the CPL nearest the lens and the ND in front is perfectly acceptable and widely used.