Looking for some suggestions a tricky spot: a corner where we have a little firepit that we need to be able to provide shade for the sitting area, but due to buried electric lines and an easement, we can't dig holes to secure the posts and it needs to be moveable if needed. The structure needs to be able to block the sun from two sides, but because of the angle the sun hits, doesn't need to be blocked from above, and we'd prefer an open top.

My original idea was to build a very basic triangle pergola like the one pictured below and putting pieces of lattice on the top part of the sides to block the sun from the sides, but I would need to find a way to anchor it without digging post holes. There is about a foot of room where we can put stakes or something into the ground to help secure it but I'm not familiar with what products there might be for doing this. There is also a slight downhill grade from the back fence to the front of the yard. We plant to have a crossvine plant growing up the structure as well so it needs to be able to support that.

It doesn't have to be fancy and we'd prefer something simple, cheap and easy to make in a weekend(was even considering using PVC pipe to make it). I'm open to any and all suggestions for designs of something that would work here or suggestions for securing a corner pergola or other similar design.

Below is a sketch of the area. Some ideas I am pondering for securing it are attaching planter boxes to the posts, putting the posts in pots filled with cement or cement filled cinder blocks, but not sure if those would be stable enough. Also curious if using lighter materials such as 2x4's instead of heavy posts would make it less likely to tip over or less secure. Thanks for any suggestions!!

The red lines are the proposed structure. Would need to be at least 8'x8' and 8' tall.

Something like this but without the fanned out boards at the top? How much anchoring would something like that need?