Here is an idea that I got from somewhere, maybe from a member of YT. Sorry I did not put down the author. If anyone recognizes this as their idea please take credit for it. Here it is:
IDEA TO KEEP DOGGIE IN EX-PEN
You could go to any home improvement store and get some crossed trellis material (it usually comes in plastic sheets or wooden expandable/collapsible sizes) and attach with some plastic zip ties at one end(as a hinge point) and simply rope/twine as needed to keep it down
I have also heard of putting a sheet over and keeping it down with some of those plastic hook & ball type things that you can use to hold babies' blankets down. (Hate it when people talk about "things" and here I am doing exactly that.

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