Answering the london system against Qb6 and follow uo Bf5

I purchased the London system opening from Simon Williams and am enjoying the attacking lines he has taught me. However, he did not cover lines such as the slav. I am having trouble with preparing a line with the moves 1. d4 d5 2. Bf4 c6 3..... Qb6. I know on move 3 I can play c3 Nc3 and I don't want to give up the white square diagional in the event of Bf5. One thing I have learned is playing f3 Nc3 Rb1 g4 and e3 building a base. I find that my king has no where to go, but that's the best I can find or just play c3 Qb3. Any thoughts?

Qc1 with the idea of c4 later looks appealing.

You can played a poison pawn variation against the London

What is the continuation after Qxb2?

I quite fancy 4. b3. I'd play 4. Nd2 in blitz but maybe not in a serious game. Why put myself under pressure of having to win from one or two pawns down? The conservative option is 4. Qc1 but 4. b3 followed by Nd2 with the intention of c4 and/or e4 seems interesting. Try to take advantage of black's lack of development by opening things up and getting pawns in the centre. I expect black's natural reply to b3 is 4. ...Bf5 5. Nd2 ...e6. After this, 6. c4 looks ok and if 6. ...dc then 7. e4 and I think white is better. Of course this was just off the top of my head looking at the diagram but I think I'd like to play it except I don't play the London as a rule. Maybe this is motivation to learn some Bf4 lines in the QGD.

"The Agile London System" is a great book to fill in the lines that Simon doesn't cover in his Chessbase videos.  It's got everything but probably isn't quite as aggressive, overall.

I have an experience using a "London" against poison pawn and I'm lose. But i dont want to discuss about how can I lose. That is the thing that i dont wanna remember.

I have an experience using a "London" against poison pawn and I'm lose. But i dont want to discuss about how can I lose. That is the thing that i dont wanna remember.

I don't like Qc1. It's the option I'd least like to play. I do like b3 because it supports c2-c4. I think the move order 1.d4 2. Nf3 3. Bf4 is more flexible for white.

In one of his books Winning with the Modern London System by GM Nikola Sedlak, (the book that covers 1...d5) after 1 d4 d5 2 Bf4 c6 3 e3 Qb6 his opinion is that 4 b3 is the best plan. He says 4 Qc1 is a possibility though. After 4 b3 Bf5 he considers 5 Bd3 the simplest plan, as played in the game Winants - Georgiev (Turin ol, 2006), that the bishop on f5 is strong and disturbs White's action on the queenside involving White's plan c4-c5-b4-b5. However, he also shows that in the game Kovacevic - Vukelic (Porec, 1998) White played 5 a3, did not put his bishop on d3, and White still managed to get a slight advantage. He doesn't like Black's ...c6 ...Qb6, believes it winds up helping White's action on the queenside.