"If I have my biggest meal post workout (as required) this won't happen right?"

That's definitely the idea. CW tells us to "eat some protein after your workout!", where really there's a fairly large 3-5 hour window where having your largest meal will certainly help. I'm coming at IF (leangains inspired) from the other end - I'm a strong guy wearing a fat suit (5'10'' down to 185lbs now ~24% BF and going strong!). I workout in the mornings in a fasted state, so I make sure to eat my lunch (largest meal) at noon or earlier to maintain muscle and burn. So far, this is actually working fantastically. I've lost ~19lbs, and yet have lost an insignificant amount of lean mass.

"What would the be the ideal amount of carbs before training. Currently I am 108lbs very lean and muscular. 17 years old."

Dude. You're ripped. How tall are you? Male or female? I can appreciate not wanting to waste away the muscle you've earned. From personal experience, I'm eating 100g-175g of dense carbs (sweet potato, cassava, yams, and fibrous veggies) on workout days, and my fatloss is still accelerating. What sort of exercise/workout do you do? I'd wager you could handle 150g-250g a day, but that's going to be up to you to decide, as you discover what works for you.