Push the slide all the way to the rear, pull the trigger....hold the trigger to the rear, move the slide forward until it stops, release the trigger, push down the 'takedown latch' as you normally would and push the slide off the frame.
Same thing GRW. Remember the part about having to pull the trigger prior to field stripping. The reason for that is, once you've racked the slide, you just cocked/compressed the striker. The slide cannot be removed if the striker is cocked. That's because the single action lever is propping up the single action sear, which is holding the striker in the cocked position. The striker has to be de-cocked prior to field stripping.
Your slide was being held back because the sear was in front of and holding the striker. Pulling the trigger will let the sear drop down, releasing the striker and freeing the slide to continue forward to the normal stop where you simply depress the take-down catch to finish removing the slide.