Let's start at the beginning, guys. There are two basic early H-S designs regarding take down, and the problem is they changed without changing the model designation. The first Model A, B, C, D and E had no button on top of the slide, and had two levers at the left rear behind the grip. They also had a rectangular button in the rear of the slide. To dismount those pistols, you push in the button on the slide, which takes recoil spring tension off the stop lug. Now the rear lever can be moved down, which will move the round stop lug straight down and allow the slide to come off to the rear.
The second type, and perhaps the best known, copied the spring capture of the Colt Woodsman. That system had not been used earlier because of the Colt patent, now expired. It involves a button on top of the slide. To dismount the pistol with that design, you pull back the slide all the way, push down on the button and let the slide go forward. In fact, you push it forward, since there is no spring tension, the spring having been captured by the pickup spring which is activated by the button. Now the lever, moved to the right side, can be turned down to swing the new type stop lug forward and down, getting it out of the way of the slide and allowing the slide to come off to the rear. Trying to move the lever down without relieving spring tension can break the lever.
The trouble is that if the disassembly and reassembly are not done exactly as they should be, the gun can be jammed up and be difficult if not nearly impossible to fix. One of the most common problems is putting the recoil spring back in without its guide; if this is done, the gun will not work and the spring will get loose and jam up everything. Sometimes patience will solve the problem, but sometimes it is necessary to drill out the recoil spring plug pin and pull the spring out to the front. This ruins the spring and if not carefully done can also tear up the slide.
Now read that all again, and see which type you are talking about.
Note that the design with removable barrel came later and solved the whole problem of removing the slide to the rear.
Jim