It is arguable that these planes are not true flying wings because things like the pilot and engine sit or dangle outside the wing airfoil. Besides Dunne's D.1, D.3, D.4, D.5, D.8 and D.10 of varying success, W Starling Burgess in the US built 19 Burgess-Dunne tailless biplanes, many of them waterplanes, e.g. the 1916 AH-7.
The 1930 Smith B2 Arrowhead was a similar landplane, backed by Glenn Curtiss (who had bought out Burgess).
The 1932 Westland-Hill Pterodactyl V was a tailless sesquiplane - a biplane with the upper wing bigger than the lower one. It flew well enough as a fighter prototype but, with the revolutionary fast monoplanes beginning to prove their worth, was obsolete before it flew.
The Easy Riser has already been mentioned.
Can't recall any others offhand, I might have missed something.