OK
So, Ill do my best. Please keep in mind that
a. I am a self taught sewer
b. This is only my second time doing this.. bear with me.
If you make one, please post pics.. I would LOVE to see it
1. Start out with a LEAST an XL sized shirt. Reason being you want the sleeves to be big because you will be making them puffy.

2. Supplies needed. A shirt, ruler, chalk or whatever you use to mark fabric, tape measure, pins, scisors and lots of patience.

3. Measure from your collar to your shoulder.. Take this number and give yourself 2 inches Mark that on your shirt. SInce this shirt is big on you, you will still have room from where the sleeve meet the armhole. In otherwords, at this point, you will NOT be cutting into the sleeve.. See in this pic where I marked it.
This mark is very important you will see why later..

4. Now, cut the sleeves off like you are making a tank or a cheesey 80s vest. now only cut around the seams of the armhole and put your sleeves to the side. You will be using them.
5. Now mark from the shouder part and go down.. but create a curve for your armhole. You want this curve to me about 3/4 of the size of the old armhole because you want your sleeves to be bigger than your armhole..
See??


NOW, pin the sides together leaving the armhole open.
Stitch up each side, staying close to the edge. Go ahead and stitch up your shoulders. You now have a fitted Cheesey 80s vest throw your fist up in the air like Billy Idol.
(NOTE YOU WILL want to cut the bottom of the shirt for length at this point, but go against that urge!!) Wait till your shirt is done to take in the bottom hem.. again, ask me how I know!!)

Now put this vest to the side.. you are going to work on your sleeves. To create a "puff" you need gathers. To do this, you will use the widest stitch on your sewing machine and sew about 1/2 inch from the top part of the sleeve.. leave the edge of your thread long because you are going to pull on these to create the gather.

Now, keep in mind this sleeve will be gathered at the bottom too, so dont get carried away.. you dont have a lot of room with these sleeves, so try to move your gatherint up to the shoulders.. like so.. Now line up your sleeve to your armhole.. You DO NOT want too much armhole.. so if you have to restretch the sleeve a bit to get it to fit, do that.. again we will also be gathering at the bottom..of the sleeve so stop stressin.

Pin your sleeves to your shirt. be sure to keep the basting stitch where it wont show on the outside.. ask me how I know this.

Sew your sleeves in.
Now, cut the bottom off of the sleeve to the length you want it to be. Give yourself about an inch.because you will be creating more gathers at the bottom.

about 1.2 inch up from the bottom of the sleeve, stitch another gathering stitch like you did for the top. Onlly this time you have TONS of room to gather so go with it.. Pull your strings and bunch it up and adjust it how you want.

Now put your shirt to the side and grab some contrasting fabric. Put it infront of you.. Take a tape measure and measure around the top of your arm, or wherever you want the sleeve to hit. For me the top of my arm was 10 inches.. so I gave myself 10.5 inches.. So cut your fabric two inches wide by whatever length your arms are.. so mine was 10.5 inches long and 2.0 inches wide. fold your strips in half right sides out and stitch the top. No need to turn inside out like a bag handle.. just leave it.

Now join the two edges of the strip and create a "circle.. Sew these edges together.. like so. Try to stay close to the edge

NOW you want to pin this to the bottom of your sleeve. This gets tricky.
You want to sew it raw edge of the strip to the bottom of the sleeve. So attach the round strip to the bottom of your sleeve and pin in place. Make sure when you pin it that when you flip the shirt right side out, it looks right. Make sure that you have both "no seam edges" touching eachother. I always mess that part up and end up witha seam from the strip on the outside of the shirt. No biggie, but Im anal about that stuff.
I hope this pic describes this process clearly.

Anyway, sew those caps in, and now you have a puffy sleeve hotness shirt.
Hope this is clear! Feel free to ask any questions!!

wait no I can be sassier than that


enjoy!