Stake out the four corners. Find a way to mark each stake at the same height. A laser level would be easiest. If you don't have one of those, you can get string-line levels that hang from a string between each stake.
Once you have 4 level marks, you can now figure where the mark should be on the high end. Figure out where you want the top of the patio to be, then subtract the height of the brick. This will be where the sand base has to come up to. Now measure from that point to the original level mark you made. Let's say that's 4".
Now figure out the slope you need for the two adjoining corners. Most say you want the slop to be 1/8 - 1/4" per foot.
So if this is a 10' patio, and we want 1/4" per foot, that'd be a total slope of 2.5". Mark these two corners at 6.5" below your level mark. (4 + 2.5).
Now for the last corner (opposite the first) we'd mark that at 9" below level (6.5 + 2.5).
You now have the 4 corners marked at the proper slope.
After you get your grave base compacted, bring in the sand, and put down screed guides to line up with each of these points. I like using conduit for this. Not too pricey and comes in long lengths. Lay your screed on these as you go along to keep a consistent slope to the sand base.
Now, with this example, the outside edge of the patio is 9" lower than the high end of the wall. That's a pretty big difference. You may want to stick with a 1/8" slope (at least along the direction parallel to the house) but either way, keep in mind that height difference before laying the patio so that the outside edges are still above grade to allow full water run-off.