Hello, this is Emily.
A clean install shouldn't be presenting you with this type of issue. Yes, the flash drive you use can be a potential issue, or the harddrive itself might be the issue here.
Here are a few key check points:
Did you create the flash drive with the Windows Media Creation Tool?
Did you boot it from BIOS and have it boot from the flash drive?
Did you choose the custom install option?
On the page where it asks you where to install, did you delete every single partition listed? Not format, but delete, until they merge into one unallocated space?