Indoor Putting Green - Not Level
Basement floors are not level if they are made right.   Throw in larger tiles and there will definitely be some ridges.   There is nothing to do to actually fix this permanently, you don't want to because the slope flows to a drain.
I would suggest that you use a trick that old carpenters used to level off subfloors for wood floors - rooftiles (asphalt shingles).   The are bigger on one end and the hold well - don't slide.   It will be painful to get this just right but I can't think of anything else I would use on something like this other than shingles.   Also you can usually pick these up cheap - find an open bag at big box or go to a resale material store and might run you $15.
You will need some heavy duty scissors to cut them and after you get things flat... if your green is still sliding you may still need some weight on it meaning you might have to lay some plywood down first before doing the green.