You can’t invert triangles.
you have to grab the landscape, rotate it upside down and sculpt upside down.
And it could potentially tank your FPS since the way the landscape works tends to kill performace.
If using world comp. Open the tile. Add a landscape to the tile. Rotate and do whatever else. You cannot sculpt them together like the flooring, but you can still add additional landscapes.
Also, you could potentially make 2 world comp levels. Then simply export the generated heightmap. Import it manually on new landscapes within the floor version like before, but if you need to edit you can now always sculpt on the “work” version, export the heightmap, and import again on tue “final” level.
as workaroudns go its decent…
also, potentially, you could do a double sided material, but it costs even more to render, so its not really a viable option.