Bricks, Masonry, Asphalt and Concrete - Patio post support bracket questions

I'm getting ready to set some 6x6 post support brackets for a large patio. The brackets I am using are the flush-to-the-surface type that look like a long "U" shape with a flat plate in the middle that lays flat on the surface of the slab.

I want to assure the brackets are aligned correctly, as I will have brackets at the house side and on the edge opposite the house. The patio cover will not be attached to the house, but instead will be free-standing.

I was thinking of setting the brackets in concrete prior to pouring the patio slab, but that is a lot more work. With a four inch slab, there would only be about four inches left to set the bracket.

What is the best was to set/align these types of post supports with the least amount of work? Is there a better type of support I could use instead?

Thanks,
Mike

The anchors you are using probably have a 5/8" wide, L shaped slot in the bottom (under the flat plate cover), which allows for some adjustment if the bolts are already poured in the cement. If there are no bolts in the cement, you can drill them exactly where they go, and use the type of anchors that you hit with a hammer, or the type that wedge in place when you tighten up the nut.