It really is a very simple block. It's made from 5 quarter square triangle blocks and 4 plain squares of fabric.
Here's a good tutorial for making quarter square triangle blocks. Using this method, I started out with 3 1/2" squares to make my 2" finished size blocks. It makes them a little oversized so you can trim them to 2 1/2" to get a 2" finished size.
You need only need 5 quarter square triangles blocks but you end up making 6 with this method. Just use the 5 best ones! You also need four 2 1/2" squares of background fabric to alternate with the quarter square triangle blocks.
A version of the Flying X block can be found in Electric Quilt's BlockBase program as #1675b.
This antique block from the early 1900's is in the Spencer Museum of Art.
Her are some ideas I have for using the Flying X block in a quilt-
|straight set with alternate plain blocks|
|diagonal set with alternate plain blocks|