Now far out of level?? If you set the baseboards level, everything will look out of whack. Make the baseboards conform to the house.
What you do will depend on the type of finished floor you will have. If you have a carpet, you can fudge a bit and raise the molding off the floor a bit to make the corners a little easier. If you have hardwood, I'd recommend a two part base system. The base molding and then a shoe molding or something similar to take up the gaps that will surely appear under the main molding.I am getting ready to put in trim. The room isn't level. How do I lay out the baseboards? Find the highest and lowest points and decide on a level to start from?