The British flag -- known as the Union Flag or Union Jack -- is comprised of three national flags built up in layers of red, white and blue. It is made up of the crosses of saints George, Andrew and Patrick -- patron saints of England, Scotland and Ireland, respectively. Making one is an economical way of celebrating special national occasions.
Cut the flag fabrics
Begin with a rectangle of royal blue material twice as wide as it is deep. Stretch a piece of white cloth from one corner to the opposing corner. Repeat the process for the other two corners. The width of the white strips should be one-fifth the width of the blue material.
Sew the strips into place. This is now the Cross of St Andrew, the Scottish flag.
Begin to add Ireland's Cross of St Patrick. This is done by cutting four pieces of bright red material to be one-fifteenth the width of the flag. Cut each piece at 45 degrees at one end. Length does not matter at this stage but ensure each piece is long enough to reach from a corner to the centre.
Draw very faint diagonals from corner to corner on the flag. The four lengths of red material will lie along these lines. For now, put them to one side.
Add England's Cross of St George. This is cut from the same red material as the Cross of St Patrick. It is one-fifth of the flag's width. Along all its edges there will be a white border -- called a fimbriation -- which is one-fifteenth of the flag's width.
Sew the flag
Calculate the width of the red strips plus the fimbriation (1/5 + 1/15 + 1/15). Using the same white material as used previously, cut two lengths to this width. One length should match the width of the flag and the other the depth.
Measure to the centre of the flag's width and position the shorter white strip so that its centre aligns with the flag centre. Stretch the piece to the opposing side, ensuring it is at 90 degrees to the flag edge. Sew into place.
Repeat the process on the short edges of the flag.
Position the two red strips for the Cross of St George exactly in the centre of these white strips, so that there is an even area of white on all sides. Sew them into place.
Return to the four narrow red lengths. Place them along the faint diagonal lines with the 45 degree edges abutting the fimbriation. Starting from the top left corner, place a length so that it is below the pencil line; top right, above the line; bottom right, above the line; and bottom left, below the line.
Sew them into place and cut off whatever excess material is hanging over the edge of the flag.