first you need to mark out the flag pattern, i did this using a pen. i marked out stripes first, then i marked out the where the stars need to go. i labled the striped R/W for (red/white) so i knew which colour to use.
for the stars, i cut lots of little strips of white felt
then cut the blue felt into long strips
i marked out were the stars need to go by putting little circles, it doesnt matter if its messy as you wont see this when its done.
for the stars ruffle the felt into small pieces like this (see picture below)
then glue them on to the pillow case with a glue gun, then when they are all stuck down start adding the navy felt, and work around each white bit and cover the square, ruffling the felt as you glue it down.
then measure the red and white felt against the stripes you have drawn, and cut the felt in to strips a little wider, then glue on in to the pillow case and ruffle the felt as you go along like the picture below
then do the same again with the white felt, and then you can put the cushion filling in.