molding tailgate shut

how would I do this without a skin? combo? or whatever. I want to have nothing in the back excpet for taillights. I wanna do this to my 4wd bed befor I put it on my truck. What all steps would need to be done to make this happen. I know it would probably be easier to use a skin combo, but I wanna try to do it wihtout one, you know, save that 200 bux.