Strain any visible liquid off crab meat, if applicable. Pick through meat to remove shells, discard any found. Set crab meat aside.
In a large bowl, whisk together mayonnaise, eggs, and mustard until smooth. Add coconut flour, salt, and garlic once again whisking until smooth and well incorporated.
Add green onions, chili, and crab meat, gently mix until well combined.
Cover and chill for 1 hour.
In a large fry pan, heat 1-2 tablespoon oil over medium heat. As oil is heating, shape crab mixture into 4 patties
Use a metal spatula to gently transfer crab cakes to oil, being careful not to burn yourself – oil may spatter. Pan fry crab cakes until browned – about 4 minutes on each side.
Serve warm, with lemon wedges and horseradish sauce.