There is a vacuum port/hole in the base of the carburetor that needs to be open for flow.

There are usually multiple "cut-outs", so that the gasket/bakelite-insulator can be placed in any orientation and the needed opening will line up.

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.