I am trying to replace my front door with a new pre-hung door. I had reservations about how this would work because the existing threshold had a sloped 2X6 under it. I also didn't know how I was going to transition from the tile floor to the new threshold. When I pulled out the old threshold, I found the tile and concrete were not even and will have to be covered (see attached photo). When I took out the frame and the 2X6, there was 2 1/2"-3" difference between the top of the tile and concrete foundation. The threshold on the new door is only 1 1/2". What do I use to build up the foundation for the door to set on and how do I cover the uneven edge in the tile and concrete?
Any help would be greatly appreciated.