I'm trying to create a sort of cup for printing. I started with a sphere and then a smaller sphere and Boolean differenced to get a hollow sphere. Then I wanted to cut an off-center hole in the hollow sphere by using a sphere or cylinder. I tried to do this again with boolean difference but now it looks like this How do I join the two together/make faces between the two layers? Or am I just going about designing this all wrong?
I think it's better do all the modelling without thickness and, once finished, apply a "solidify" modifier that will give you the needed inner face. Also the booleans operations, as they create "bad" geometry (triangles, Ngons, no edge loops) should be avoided if possible: the image illustrate a quick way to join a circle (8 vertices) to a mesh sphere (Bridge edge loops) and the result after subsurf and solidify modifier, 2 minutes of modelling.
Another shape obtained with the solidify + subsurf from an UV sphere:
Two methods come to mind instantly. The first is manually, where you selest one or two vertices on one loop, either the inner or outer, then select a vertex (if you want the resulting face to be a triangle) or two (if you want the resulting face to be a quad), continuing aroud the the edges until the two loops are bridged. Another may require some fiddling. Select a segment of the loop around the hole in the inner sphere and a segment of the loop around the hole in the outer one, select the two edge loops, and bridge them. The fiddling will be obligatory if the inner and outer loops do not have the same number of segments.