Firewall flange dimple?

I'm working on drilling the hinge, shim and sides to the firewall flange and my firewall flange is not dimpled, did I miss a step? It has to be dimpled or ???

Joe

Once you have fitted the hinges for the cowling, and match drilled everything you can dimple. If you dimple the flange first, then try to match drill the hinge, the dimples make it hard for everything to fit together flush.