Diagram showing step-by-step construction of the Union Jack Flag, as described in the blazon as decreed by George III of the United Kingdom on 1 January 1801: 

"The Union flag shall be azure, the crosses-saltires of St. Andrew and St. Patrick quartered per saltire counter changed argent and gules; the latter fimbriated of the second  [viz., argent]; surmounted by the cross of St. George of the third (viz., gules), fimbriated as the saltire (viz., argent)." (Source: The European Magazine: And London Review, Vol.39, Philological Society of London, 1801, p.74 [1])
Own work
Lobsterthermidor (talk) 17:43, 19 February 2022 (UTC)