4/ With the help of the Graphite modelling tool bar, on the Selection tab, choose the selection by Numeric, type a value of 5 and select “<” option, that way it will select all vertices that have less than 5 edges connected to them.
Then, invert the selection.
5/ Still in sub object mode “vertex” hold CTRL on the keyboard and click on “Edges”, it will select all edges connected to the selected vertices.
7/ Select all polygons, hit the menu icon next to “Inset”, choose “by polygon”, put the desired value.
8/ Leave the sub object selection and add a Mesh select modifier, choose polygon, it kept the selection history from the edit poly sub object mode.
12/ That’s it. You can play with the number of segments in the shell modifier to get sharper edges on the holes.