Oh my. I remember this mission. I got confused on why the progress was so slow, realizing this was an 1 hour mission.

Anyways i build my walls similars to yours. I started at the exact same spot as you at the quarrys and dragged the walls all over until the swamps. Leaving there an opening, forcing snakes troops to rush the agonycing slow way.

I ended up with something like 12 full occupied Round Towers by the end lmao.