First, measure your mailbox across the top (curved edge) and across the bottom. I drew this on a paper after I measured and then drew out what my cut piece of felt would look like, since I needed to account for the flag attachment. My mail box was 21" across the top and 18" across the bottom length. I planned on adding 2 inches to the long side so when it went across the box it overlapped at the bottom, but I forgot and it worked out better without it actually.
Then I cut my felt 18" by 21"
The cut piece:
Measure up and over for the hole where the flag goes. Mine was 2.5" by 2" and 2.75" up from the bottom. Cut the flag square out.
I wanted baseballs and stars on my cover, to go with our ball theme. So I traced a lid onto white felt and cut out 2 baseballs.
One for each side:
I used the lid to make the lines where the laces go and then I used red thread (4 strands of regular thread because I didn't have red embroidery thread) to make the laces by hand.
Then I left out where I cut out the stars and sewed everything on. I also added super strong magnets to each corner (you can see where I sewed squares) I just cut squares of felt a little larger than the magnet and sewed 3 sides then stuck the magnet in and sewed it shut. Now it just sticks to the mailbox! Much easier than my original plan of sewing ribbons to it.
This was really easy and could be done for any themed party! I think it will be too cute outside with some balloons, of course!