If your benchwork is able to support it, use door hinges, the kind with the removable hinge pins. My old club in Mobile, Al has a layout that has had these pins in place since 1981. My current club has used them on both of the modular layouts we've had since 1989.
If you use something for the benchwork edge, like a 1x3, etc that is to say, something smaller than a 1x4, you can beef up the corners befoore the hinges are attached. Place a 2x4 block in the corner, cut to a 5-6" length, and attach it to the back side of the corner, running "long ways" with the longer sides of the module. Then attach the hinges, using a slightly longer screw than they come with.
To attach the hinges, you have to first attach the modules together, using C-clamps. The spring clamps aren't strong enough. Make sure the modules are level with each other, both length and width, that the roadbed and track, we used 6" pieces of Atlas snap track as joiner tracks, is smooth with no bumps or elevation problems.
Take the hinges, still assembled, and place one side on a module, with the hinge pin splitting the joint. Use a small level to make sure the hinge is level, mark an outline of the hinge and mark for pilot holes on one side. Remove hinge, drill the pilot holes, put the hinge back on the module using the marked outline and pilot holes to position exactly, and screw that side down. Then just flatten the other side of the hinge against the other module, and drill the pilot holes, and screw into place. Repeat for the other side. Wash, rinse and repeat for all the other modules.
Using this method to assemble our layout, we can start on assembly, and then be running trains in less than 40 minutes. This is a 4 man crew, assembling a 20'x30' layout.