ᐅ Is it possible to lay patio slabs on gravel over an old foundation?

Hello, as the title says, I want to lay new patio slabs on gravel.

The old slabs are 5cm (2 inches) thick and were glued to the foundation. The new slabs are 2cm (0.8 inches) thick.

I want to lay them on gravel because I also want to widen the patio. For that, I would of course need to work with crushed stone and gravel.

Is this safely possible, or what would be the best way to proceed?

Of course it works, just compact properly

If there is a slope, use a drainage mat as the base layer, followed by 3-5cm (1¼-2 inches) of gravel. Otherwise, create a slope using screed. Important: do not omit the drainage mat. When connecting to the widening, compact carefully.

Is a drainage mat only necessary in the part with the foundation, or is it needed throughout?

*edit* There is a slope present

Only for the foundation. The planned widening with frost protection gravel about 40-50cm (16-20 inches) thick. Moisten the gravel slightly before compacting, vibrate it, and then vibrate it again the next day. This will prevent any settling even after 10 years or more.

Thank you :-)

I will start taking care of everything gradually.