Gut the flounder, clean, cut off gills and fins, drizzle with lemon juice and leave for 10 minutes. Slice finely the bacon, chop onion in semicircles, chop dill. Melt the bacon fat , fry onion, remove it from a pan. Season fish with salt and pepper,flour and fry in the fat, add onion and heat. Serve with dill and slice of lemon.