I have this object, what is the best way to get the faces created?
I hope that makes sense.
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One way to do this is with the Boolean Modifier.
Now select your contour object (which is now a plane) and add a Boolean Modifier. Properties window > Modifier Properties tab > Add Modifier. Then choose Boolean. Then as Object choose your cut out object and click Apply. If you have multiple separate cutout objects repeat it for every one of them.
Don't want to use boolean?
Make sure all geometry is part of a single object.
In Edit Mode, use F to create edges between vertices, around your cutout geometry.
Use Subdivide to have the surrounding geometry have an equal number of vertices as the cutout geometry.
Press Ctrl + E (or click the Edge button), and select Bridge Edge Loops.