I was just bored, and decided to go ahead and do this. Feel free to use it in any British ships, or whenever you really really need to colonize something, just be sure to credit me! Comes in multiple sizes!

Possibly my favorite naval ensign, St George's Ensign (or the White Ensign if you don't have much time) has a storied history. The first use of a recognisable White Ensign was in the 16th century, which had a much broader St. George's Cross (the red plus) across the flag, and a smaller St. George's Cross in the canton, or upper left corner of the flag. Around 1630 the larger cross was removed, though it was added back and made slightly skinner in 1707. In this year, the Union Flag was added to the canton. The ensign took its modern form in 1801, when the new Union Jack was added to the canton, with a deeper blue to prevent fading.

Now get out there, and colonize some innocent countries because, well,
you have a flag!
(https://www.youtube.com/watch?v=UTduy7Qkvk8)