I'm a first-time technical director bumping in my set tomorrow. I am building a boxed set for the March Family living room in Little Women. I have a long back wall upstage and 2 lateral walls, stage L and stage R (12 ft. each). The upstage wall has a 6 ft. entry-way and a window seat. The lateral walls each have a doorway. My question about bump-in is where do I start? I am going to be using ledgers to adjoin the flats b/c my flats are out of square (high school students constructed them). Do I start with 2 corner flats and work out? Or, do I lay a lateral wall face flat on the ground, ledger them together and then stand the whole thing up to brace to the floor?

Any other tips would be greatly appreciated.

Thanks,
Kim

Firstly I'd mark out a centre line, on the stage, using a chalk string. Which I'm sure you can borrow or purchase for a few $'s.
As Vicki suggested utalise your book flats & build from there. Using your french braces [jacks]
Check the proscenium setting line, where the house curtain travels or drops in.
I normally set up the upstage flats, [centred] then work the OP & PS. Check out the sight lines for each side wall angle.Use a return flat on the downstage end of the side wall, to mask off. Especialy if the house rag travels near the end of the flats & can foul upon when billowing out.
Then set the ledgers & secure the bracing, when your happy with the settings.
{I see you picked up one of our theatre ockerism terms -"Bumping IN"}