There is a spring loaded block under the barrel- just above the hole where the take down lever goes.
Some how?- you will have to push that down enough to get the end of the slide over it in order to to remove the slide.
See in the pic just above the take down lever. There is a "spring loaded" bar sticking up- IF that bar is there and did not come out when you removed the take down lever- you will somehow have to depress (mash is down) in order to get the slide back towards the rear far enough to be able to lift it off the rails.
BUT- If that spring loaded bar came out with the lever- then the only thing that can be holding you back is the hammer. If you pull the hammer back til it locks- and then pull the slide back to the hammer- you still have to overcome the remaining spring tension on the hammer.... put a little more pressure on it and see if the slide will move farther to the rear- IF SO- then you should be able to lift it off the rear of the frame, then push forward and remove.