Go get some 1" PVC to make something like an open-sided box that you can set that screen on top of, and then you can ziptie the screen down to the PVC.
Then you can secure your PVC "box" to the ground with bolts, zipties, weights (books, etc) so that it doesn't get lifted up as the plant starts to grow in it.
Edit: You probably don't even need to use 1"PVC. I'd use 1" for the base to give it some weight and maybe 1/2" for the top where the screen will sit. And go ahead and use PVC cement to make sure it sticks together. PVC is cheap that even if you screw up and glue something wrong you can re-build for a few bucks.