Bricks, Masonry, Asphalt and Concrete - Slab Patio

Im am wanting to remove the existing cracked concrete patio and repoor....the problem i am running into is that i only have one open side....the slab will be touching walls on the other three sides so i am unsure how to screed correctly. I have only poored concrete with two or more sides open. Help? any sugestions?

First, chalk some lines on the walls at the intended height of your slab. Remember your slope for water runoff. Next, using the lines as a guide, place expansion joint material against all three walls. When you pour, use your hand float to float a "wet streak" along the walls at the height of the expansion joint/chalk lines. Cut a straight 2x4 so it will fit between the two parallel walls with a few of inches to spare.
Have one man on one end of this "screed board" and another man on the opposite end. Use the "wet streak" as a guide and run your board off of that. You'll have to be careful not to dig in. Just hold up on the screed and let it ride on the wet streak. Don't worry about small humps and dips, the bullfloat should take them out. Good luck.

Pecos