We have a small platform attached to our fence we put birdfood on. However the chonky pidgeons and roudy jackdaws manged to break it! So i designed something similar with double the mounting holes.

Printed at 20% infill and 4 walls because i have some chonky guys to feed. so might be overkill for some! it also scales quite nice if you only have smaller birds.
No need for supports when printed with the rear on the bed. Came out nice and sturdy and some standard drywall screws grip the plastic and fence post nicely. I printed it in blue pla because that what i had and because birds are attracted to blue. Who knows how long the pla will last outside. We will see!