The propane tanks have to be secured in a seperate room with ventilation through the floor and all possible cracks have to be sealed with rubber strips. The tanks have to be fixed with compression belts and the pressure regulator may not be older than 10 years.
To make sure that the lid can be properly connected, extra slats have to be glued. If there is no room to use clamps, you have to improvise.
Kreg-connections and glueing are my favorite methods of connecting. Clamps are indispensable.
The propane room has to be sealed at the sides and on top with rubber tape. In the floor there has to be an opening to give the more heavy propaan opportunity to escape in case of leakage. I have a pressure regulator for 30 mBar.
I used 8 mm flexible copper tube which runs directly to the stove in the kitchen unit. It is important to check all compression fittings with (Griffon) gas leak detector. .