In todays daily mirror a reader asks..."what part of the Union Jack represent Wales"
The flag of the United Kingdom, commonly known as the Union Jack (which derives from the use of the Union Flag on the jack-staff of naval vessels), embodies the emblems of three countries under one Sovereign. The emblems that appear on the Union Flag are the crosses of three patron saints:
the red cross of St. George, for England, on a white ground
the white diagonal cross, or saltire, of St. Andrew, for Scotland, on a blue ground
the red diagonal cross of St Patrick, for Ireland, on a white ground.
Wales isn't represented because when the Union Flag was first thought up by James 1 (or VI, depending on your point of view), Wales was seen as a sort of appendage of England, rather than a separate land like Scotland or Ireland. Sad but true.
When I was in the Brownies we had a three piece folded card which showed you how each part of the flag sat over the previous one to get the end result.
Wales has been treated as part of England since 1301, when Edward I created his son Prince of Wales and established the Council of Wales to govern the Principality. To this day, a reference to 'England' in legal documents is taken to include Wales.
The flag was created over later time, and therefore has no speccific reference to Wales on it.