Heat the oven to 375°F with a rack in the center. Line an 8 1/2-by-4 1/2-inch metal loaf pan with parchment rated for this temperature, covering the bottom and long sides and leaving lifting handles. Rinse the fully cooked navy beans, drain thoroughly, and weigh 480 g after draining. Spread them briefly on a clean towel to remove clinging droplets; do not squeeze them dry.

Place the drained beans in a food processor with the eggs. Process until smooth, stopping to scrape the bowl and blade area as needed. Small flecks of bean skin are fine, but eliminate whole beans and visible egg streaks. The mixture should resemble a thick, smooth puree. Do not taste the raw mixture. Wash hands and food-contact equipment after handling raw eggs.

Transfer the puree to a mixing bowl. Fold in the oat flour with a sturdy spatula until evenly incorporated, scraping across the bottom so no dry pockets remain. Expect a thick, scoopable batter that holds soft ridges and slowly settles. It will not form an elastic dough. Scrape it into the prepared pan and smooth the surface, pressing gently into the corners. No kneading or proofing is needed.

Bake for 60 minutes, checking at 50 minutes. The top should look dry and feel firm, and the center must reach 200°F on an instant-read thermometer inserted into the middle without touching the pan. This center temperature also exceeds the minimum needed to cook the eggs safely. If the top darkens early, tent loosely with foil. Expect modest expansion and a low, dense loaf.

Cool in the pan for 10 minutes. Using the parchment handles, carefully lift the loaf onto a wire rack, remove the parchment, and cool for another 50 minutes before slicing. In surroundings above 90°F, complete this second cooling stage in the refrigerator. Cut into 16 slices for 8 servings of 2 slices each, then refrigerate promptly in a covered container.