What's the most effective way to align 1x1 tiles? There are a number of sets (e.g., the Farnsworth House and the Parisian Restaurant) that use a field of 1x1 tiles to represent a tiled floor. I have found aligning these pieces such that they are all square to each other to be a challenge. What techniques can I try to achieve a nicely aligned grid of tiles?

For example:
I will sometimes take another piece, i.e. a 1x4, next to the row I'm about to place so it helps align it. Then use the brick separator's flat end to adjust the 1x1 as needed. But I'm a little ocd about the tiles being lined up...