Guild Wars 2

I was trying to make a jumping puzzle in our Guild Hall but I have a really hard time to build anything because I always get the note that the surface is to uneven. It works to build horizontal (kinda after 3 tabeles and some chests it’s over) anything else seems just impossible. Any tips or tricks?

Boxes are your friend. Then its a matter of searching for the 1 pixel that allows you to place it.