Among those flags, one of the most commonly found was the following:

How is this design done? Pick the current flag and remove the blue. But, differently from popular knowledge, it's not 100% free of "Scottishness".
As I antecipated in this article, the strange look of St. Patrick's cross (the red saltire i.e. diagonal cross) is due to its merge with Scottish St. Andrew's cross. What a parcel of media forgot was that, without Scottish saltire, the flag would look like this:

This layout is, by far, bolder and more equilibrated. Obviously, many other design could be taken into consideration, and media did it; some of them kept the blue, others added elements to Wales and, more rarely, Cornwall.
Comments are welcome!