Have you ever wanted a completely playable defense against 1.d4 and all the Flank Openings, that also has very little theory? Then look no further; the answer is to play the Janowsky Defence to the Queen’s Gambit Declined with 1.d4 d5 2.c4 e6 3.Nc3 a6.
The threat to capture on c4 and then protect with …b7-b5 pretty much obliges White to capture on d5 (4.cxd5 exd5) after which 5.Bf4 is the main line. But can’t Black then play 5…c6 followed by 6…Bd6? This is analogous to the line 1.d4 d5 2.c4 e6 3.Nc3 Be7 4.cxd5 exd5 5.Bf4 c6 6.e3 Bd6 but with Black having ‘gained’ …a7-a6 instead of playing two bishop moves. I don’t see this as being a particularly bad thing as the pawn move can help defend against potential minority attacks.
Here anyway is a sample game: