In a medium mixing bowl, gently combine the crab with the mayonnaise, celery, onion, lemon juice and ½ cup of the panko. Be careful not to break up the large pieces of crab. Season with salt. Shape into four 1½-inch thick crab cakes.
Spread the remaining panko on a plate. Gently press the top and bottom of each crab cake into the breadcrumbs (not the sides). Transfer to a large plate and refrigerate for at least 1 hour.
Preheat the oven to 350℉. In a large ovenproof nonstick skillet, heat 2 tablespoons of oil until shimmering. Cook the crab cakes over moderately-high heat until golden brown on the bottom, 3 to 5 minutes. Gently flip the crabcakes and transfer the skillet to the oven and bake for 10 min, or until golden brown and hot throughout. Serve right away.