a pic of your set up now would help to see what you have to work with
I'm redoing my duck/chicken pen now. We cut a bunch of wood today for my proof of concept and have the plan going forward. I'll get the rest of the wood and a new saw blade later this week so we can finish cutting the rest of the wood so it is ready to just start installing.
I already have 4x4 posts in place, but for this project, we are going to extend them which is what all the new wood is for.
I'm using 2x4 welded wire fencing that is 5' tall and then adding an additional 2' of lattice on top so I have a 7' fence.
I will then dig out a bit around the pen and lay down some folded field fencing (which was around the area we are going to use) to prevent anybody from digging under.
We do have hawks, so I think I will be stringing line across the top to keep them out if they decide they'd like an easy meal.
The welded wire fencing is ~$1/foot
If you have green t-posts, you can use that, but we are using wood this time (their current pen uses t-posts). Current pen also has several layers of e-fencing around it. The new one should be enough that we no longer need that.
Their new pen will be about 25x25 which is a little bit bigger than what they have now, but it will be nicer looking than their pen now which was the reason for this project.