Are you mixing up the adhesive, using a thinset or versabond (has a little more give than thinset, but I still have cracks in the tiles now)? Sometimes you can go over the area with thinset and fill that spot level. Do that first, then use the rest of your bucket somewhere else in the room. After the leveling patch has dried then treat it like floor when you get to that point and put down your adhesive mix over it like usual. This works best if the spot to level (the indent) isn't a very large section. Otherwise mix up some of the specialized floor leveling product and pour it over the area.