Easy!

With a long run of 1/2" rope, I run a "ridge" line between two trees, secured to the tree with two turns of the rope and finished with a clove hitch. It looked like a ridge of a house.

Then, for the corners, I ran some 550 para cord through the grommets to some more trees. Very stable.

We put a couple of poles (logs we found) inside to get a little height in the middle.

This Ridge Rope technique really works well for me with the big tarp, once you get that center lifted you don't have to work to hard to get the corners right.