I was working with a boys XL but really any size will work I think. Please read all of the directions before starting.
1st. Remove both the Button strip and Hole strip from shirt. These will be the waist band.
2nd remove the arms and collar. When doing the collar cut as close to the seams as possible to try and make fray minimal.
3rd take apart the shoulder seam.
4th fold over the top back of shirt to form the neck of apron. create pleats until it is the desired width. this will vary depending on the size of shirt. you don't want it to be too wide or else it will balloon out in front. you may want to skip ahead to step 8 and 9. just pin the collar in place to see if your width is correct.
5th fold down sides and pin.
6th trim sides and cut the bottom of shirt straight. you may want to have the collar pined on so you can try your apron on to make sure of the length. keep in mind you will be adding a 1/4 yard to the bottom.
7th sew down the pleats at the neck. next finish the edges of your apron. the is no need to finish the bottom (that is done in step 10).
8th separate the collar.
9th sew button side of collar on ride side of apron. sew the extra button, from the inside of shirt, on the other side of apron, to attach the collar.
10th iron a 1/2 inch hem on apron. and then mark the 1/4, 1/2 and 3/4 points of hem.
11th mark the 1/4, 1/2 and 3/4 points on a 1/4 yard piece of material. Pin to apron in coordinating spots.
12th zigzag the two pieces together gathering as you go. be sure to zigzag them right on top of each other because this will prevent them from fraying. not that, that matters because there is going to be a lot of fraying going on.
13th finish the end of the button hole strip. the strip with the buttons doesn't need to be finished because it goes under, but if you want to you can. now button the two strips together. i made mine so that it buttons three times. then with the apron on wrap the strips around and pin them to the sides. it may take a couple tries to get it the right length. as my dad always says, "you're not building a piano." so it doesn't need to be exact.
Then you're done and you have this really cute apron. please post any questions.