Umm... I think that's not exclusive, we can make BL2 levels using the available objects. I had the same doubt before but I now know. You can open some levels in level world in level editor and check, or just check while playing
You don't, you just make a BADLAND 2 themed level. BADLAND 2 has a certain distinctive design style described by some of its new hazards as well as noticeably a more "layered" design consisting of protrusions carefully and uniformly placed on an object. All of which as suggested, involves simply layering, which means using more than one object stacked on each other to achieve the effect.