Pour 1/2 cup of cold water into a large bowl and sprinkle 2 Tbsps. of gelatin over the liquid.
Add 1/2 cup of boiling water and stir the mixture constantly until the gelatin has fully dissolved, about 1-2 minutes.
Scoop 2.5 cups of birdseeds along with optional add ins into the gelatin mixture and stir together until all the seeds are well coated.
Continue to stir until there is no liquid puddling at the bottom of the bowl. This should only take a few minutes.
Prep the cookie cutters by placing them on a large cookie sheet lined with parchment paper.
Once the mixture is ready, firmly pack the cookie cutters with the birdseed mixture.
Make a hole in the ornament using a stick (about the size of a drinking straw) about 1/2" down from the edge of the ornament.
Place the ornaments in warm place to dry for 24 to 48 hours. Carefully flip, or put the ornament on its side so that the bottom can dry too.
Once the ornament feels dry, carefully press it out of the cookie cutter and remove the stick.
Pass a string through the hole of the ornament and hang on a tree outside.