New answers tagged plastic
That appears to be intended to pry out with a screwdriver or similar flat tool at the indents a little past 6 o'clock and a little past 12 o'clock as pictured.
There are no regulations or restrictions for temporary bathrooms. You can do whatever you want. What you propose seems fine, certainly better than newspapers (old roommate put newspaper in our bathroom to walk on so we didn't have to clean the floor - don't ask how it turned out).
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