In the meantime, here's a link we used when siting flicker nest box l year or so ago. We had at least two, and likely more, flicker families raised in or near the nest box this year. .. so quite successful. Be sure to pack the box with wood chips so your local birds can excavate.
Ours were set about 15 feet high, but note that the suggested range is 8-20 feet...you have some flexibility so can evaluate clear flight zones, etc. and you will want the option to check and clear out the box yearly, refilling with about 4" fresh wood chips.