I came across this pencil bag on Pinterest back in December. It was very similar to a pencil bag they were selling where I worked, which I had been thinking of trying to reproduce. Fortunately, there was a tutorial. Unfortunately, the website is in a different language (maybe Chinese or Japanese).
Since there were pictures, I was able to see how the bag was constructed, but I came up with my own measurements and method. It sewed up very quickly, I believe it only took me about 20 minutes to make it. It is definitely an easy gift idea, great for art supplies or make-up.
I made mine with two layers of regular cotton fabric, and it holds its shape really nicely. The secret is how the ends are sewn together.
The bag is really just a rectangle that is made into a tube when the zipper is sewn to the long sides. I started by cutting out two 9" by 13" rectangles, and stitching them together, with the wrong sides on the inside. Then I sewed on the zipper along the long edges. Then while the bag is inside out, I pinched the center of the sides together, and then pressed the bag flat.
Then I sewed across either end, making sure not to hit the metal ends of the zipper (That would take out your needle for sure). When you turn the bag right side out, iit makes these neat triangle folds at the ends. They make it look interesting and give it the structure to keep its shape. Fill it up with colored pencils, and it's a great gift for your favorite art lover.