I blend up a couple dozen eggs (not cooked) at a time, pour them onto silicone mats in a dehydrator, then once they are dry, I run them through the blender again to turn them to powder. I have one of those little gadgets that you put on the lid to vacuum seal the jars and I add an oxygen absorber to each jar.
I think poured onto parchment paper on baking sheets in the oven on its lowest setting would work as well, but I bought a small 8-tray dehydrator for about $100 that lives in the garage and use it to make fruit leather, dry herbs and mushrooms, make tomato powder, and so on so it was worth having one.