Do you have a floor grinder? Do you have dust control? Do you have a 10ft level to use to investigate the amount of problems you have to deal with? Do you have the materials purchased? Do you know how to bond old concrete to new? What are your skills?

Concrete is a little tricky (because you need to know many many many things about stuff most of us NEVER touch....ever). It is not rocket science but it is tricky. It takes a deft touch and a good sense of timing and how well a material is mixed...how to mix it....what is better, tap water or distilled water?

So many things can go wrong...but most don't. You have some deeper patches which need to be roughed up a bit (do you know what a broom finish is? or how to achieve it? and why?). Then the correct amount of material needs to be mixed and applied.

The REALLY fun thing about Self Leveling Compound (SLC) = it is NOT self leveling. You have to work it and know when to stop.

Is there a reason why you MUST DIY this? Is the bathroom inoperable? Is the toilet sitting in another part of the house? Is the shower DOA?

If you can hang on, you have more work than you think you have. Carpet hides HORRIBLE subfloors. I can see rolling concrete in the background of the last photo. That means most of your floor needs coating...not just the damaged are that used to have tile.

Here's a hint: LVP requires a flatness rating of 3/16" over 10ft. That's flat...and vinyl does much better with a GOOD subfloor than a 'just good enough' subfloor. Your subfloor needs to be brought up to the 'just good enough'. You must assume you will have to deal with the areas that used to have carpet.

As soon as you get your 10ft level out, you will see what I mean.

As suggested, get yourself a 10 foot level or straight edge and a grinder first. Take material off and inspect. Sounds like the contractor did not want to remove the old thin-set mortar, instead chose to pour SLC over it. Your flatness will most likely come in true by removing the old thin-set. Homes are built with fairly flat floors, not perfect but fair. How many square feet is the new floor install? How many square feet of the SLC is poured in?

Total square footage is 450 SF. SLC was poured over about 150 SF where tile was previously.

So yesterday we went around the space checking the level and there are only two bad areas. One has a high spot that we tried grinding, with little success (angle grinder just didn’t seem to cut it). The other has a low spot which we filled with self leveler. The low spot is a lot better, but still a little low. We were thinking of trying to chisel the high spot (it’s a really small area and it’s where I know thin set wasn’t removed) and then self level the low spot again and any damage from chiseling. Thoughts on this plan of attack?

Get a 7” angle grinder and a 16 grit daimond. Hook it up to a shop vac. You will be able to remove the thin set without a problem. You will need to keep up with cleaning the filter on the shop vac to prevent clogging.