Echoing Littlebirder, you can build a nest box in about an hour from a
2x6.  If you search on Google for "flicker nest box" you get a link to a
Washington Department of Wildlife page
(https://wdfw.wa.gov/living/projects/flicker.html) which has the simple
instructions.

I did this a couple years ago and it worked well.  Key is to stuff the
box with wood shavings or sawdust; apparently the act of digging out is
essential to Flickers for nesting.   Oh, I'd leave the other deterrents
in place, just in case.

--
Jim Beneteau
Arlington, Wa