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Do the slab as structural floors (thick) and the floor finishes as architectural floors (thin). Specify materials in the type properties of the floors.
Use a thick structural floor for the slab of the whole floor, and individual architectural floors with different materials, for the rooms, on top of the structural floor.
Another method is to use Parts. Create a Floor, edit the Structure and add compound "layers" as required-- such as concrete slab, topping, etc.
Then select the Floor, and Create Parts. Then use Divide Parts, and sketch different regions / patterns where you need
flagstone or carpet. Finish the sketch. Then apply different Materials to the Divided areas.
In View Properties, you need to select Show Parts and/or Show Original or Both--experiment with these settings
to achive the desired display behaviour to show the Divided Parts with your flagstone and carpet Materials applied to them. You can Schedule the area of Parts and Materials as well.
Using Parts for floors is just another method to have multiple materials/patterns. You can model individual floors as suggested by Alfredo as well.