Hi, sorry about all of the posts lately. OK, I decided to make my map again from scratch and I'm wondering how to attach bases. I'm on GMax and I simply thought of linking the base to the skybox but that doesn't work. Please help.

No, there's an "Attach" option when you select the object. I do believe you can use it to connect one object to another, but as to physically attaching the base to the ground, without overlapping edges, you'll have to delete the faces underneath the base, and then place the base there, and recreate faces to readd the ground you removed, so long as it doesn't go underneath the base. That avoids the overlapping faces...