if you are a complete beginner it is easier to put on muscle in the first several months of training.

You can put on 6-10lbs easily but of what? I'd say it is hard to put on 6lbs of pure muscle. If you add creatine that will add weight and volume but that is because it pulls water in to your muscles.

heavy weights 2x a week
boxing 3-5 xs

to gain muscle from these workouts you will need to eat and rest a whole lot.
If you did a bodybuilding type routine that would be more like it.