There is no need for a pattern. It is a simple modification that can be altered to fit any size and any style.
This is an excercise in sewing freedom. No rules, no patterns, no pins, no worries, no one to tell you it shouldn't be made a certain way. It's free form stitching, It's all you, have fun! That is the beauty of altered clothing.
Step 1: Find the Skirt...
This skirt was an Old Navy style purchased at a thrift store and altered in an hour. Embellishment take a little more time. The ruffles at the bottom of the skirt are sewn with fabric that was torn and gathered rather than hemmed so it fits nicely with the shabby style.
1. find a skirt with a matching fabric liner
2. Cut the liner out of the skirt and save it.
3. turn the skirt over so that the back is facing up and cut it down the middle from top to bottom (so that when you open the skirt it is no longer a tube but can open out all the way)
Step 2: Straps & Pockets
1. have a friend help you measure from the center of your back between the shoulder blades up and over your shoulder and down to the top of your chest. This is how long your straps need to be.
2. decide how wide you want your straps (mine are about 3 inches wide) and cut a couple of strips from the lining material that you cut out of the skirt. apprx 3" wide X "your measurement" long. You can make extra strips and sew them together for a layered style and even add a contrasting fabric scrap between them for more definition as I did with the tan fabric. I even used a contrasting color of thread for a little more detail. ends of thread were left uncut on purpose for a tattered look. Edges of fabric are left unhemmed to aid that style as well.
3. To attach your straps you will sew them to the front top of the skirt. Now take the back ends and criss cross them, sewing the right strap to the back left corn of the skirt, and the left strap to the back right corner of the skirt. This crosses the back edges of the skirt that was cut down the center to form the overlapped back of the apron.
4. to create the pockets you just decide how big you want your pocket and cut a rectangle of fabric from the liner material and stitch it on three sides to the front of your apron, no need to turn the sides under unless you want to. You can add contrasting fabric to the front of your rectangle as I did or not. Add a fabric rosette, cloth flower, decorative pin, rhinestone whatever you want to embellish your apron with.