What is the fastest way of doing this kind of feature?
there is a very old feature called Slot
Go to Reuse Library, It's available under 2D Section Library but with different name. You can change the dimensions as you needed.
Regards,Ganesh#IngenuityisNX | NX Continuous Release F.A.Q | NX12.0.2 Measurement Commands Consolidation
you can also create your own reusable object that subtract the slot shape from your model.see in the reuse library the snap example how you can doe that.