How about a pic? I took plenty of them when I was installing--took that camera everywhere. In this case it was an engineered floor around a tiled area that had a vertical difference of 3/8" from one side to the other. In order for the t-molding to site flat I had to ceate a makeshift screed so the amount of floor patch would be consistant all the way across. Butting the hardwood to the tile after the floor prep in this job wouldn't have made sense because the tile cuts were irregular.
It looks like a concrete subfloor in your pic--I wouldn't suggest patching compounds for wood subfloors. Take the thickness of the flooring(using as a guide) and rip or cut a notch out of the end of a straight piece of lumber. In this case a four foot piece of flooring was used. This will allow the right amount of patch to be used in the area. Mix the patch, dump in front of the screed and pull it back over the work area.
Also it looks like a solid hardwood in your pic? I'd be real careful with that one on a gluedown if you want to butt the flooring against the stone. If the conditions aren't right failure is likely.