almost magic phone cozy tutorial

This is just one way of making a phone cozy.
I've combined a few ideas to make something that would suit my husband (and it was his idea to include a strap that would make it easier to pull the phone out but also to help secure the phone inside).

Since there are so many phones of various sizes, the tutorial does not give you measurements for one specific model, but a method to adjust the measurements according to the size of your phone.
So measure your phone (or check it up online) and let's assume that for the purpose of this tutorial:
WIDTH = width of your phone + 2 x thickness of your phone + 1/2"
LENGTH = 2 x length of your phone + 2 1/2"

Having that in mind, cut:

- 1 piece of fabric for the outside of the cozy - WIDTH x LENGTH
- 1 piece of felt for the inside of the cozy - WIDTH x LENGTH
(optional, not pictured, 1 piece of batting - WIDTH x LENGTH)
- 1 piece of fabric for the strap - 2.5" x LENGTH (or longer, please read Step 3. before cutting)
- 1 piece of fabric for the "stopper" (I will explain later) 1 3/4" x WIDTH
NOTE: 1/4" seam allowance used unless stated otherwise.

Step 1.
Take the outside fabric and the felt lining, put them on top of each other right sides together and sew along the top and the bottom.
(if you want to add batting to make the cozy thicker, just put it on top before sewing all the layers together)

Turn inside out and press.

Put aside for a moment.

Step 2.
Take the strap fabric, fold inside 1/4" from each side, like this:

then fold again in half lengthwise, press or pin.

Topstitch along the long edges.
Take the "stopper" fabric (i.e. the smallest piece) and repeat Step 2.

Step 3.
Now we have to decide where to affix the strap.
Take the "body" of the cozy and fold it in half with the felt lining outside.
Take the strap and position it in the place you'd like to stitch it on.
If you cut your strap the same length as the "body", I would advise affixing the strap between 1 1/4" and 2" from the bottom:

(disregard the fact that the photo shows the strap folded under the "body")
Here I put the strap at 1 1/4" from the bottom, which resulted in the phone sliding just very slightly out of the cozy.
Generally, the closer to the top you affix the strap, the more the phone will slide out when you pull it, and you might decide it is more covenient for you to have it slide out more. Just remember that if you want to sew it higher your strap needs to be longer.

Mark the place /pin the strap where you want it. (If you pin, make sure that you pin to the felt lining only, unless you want the stitching to show on the outside). To prevent fraying you can fold slightly more than 1/8" of the end of the strap under before stitching.
Unfold the "body" and stitch the the strap to the felt.

It should looks similar to this:

Step 4.
Let's move to stitching on the "stopper" - i.e. the short piece of fabric that will stop the strap from sliding completely out of the cozy and making it hard to put the phone back in.
To find the place where to stitch it on, turn the cozy over so that the place where you stitched the strap touches the table.
Put the "stopper" about 3/4" from the top of the cozy and mark the place/pin.

Using the strap as a guide, stitch the "stopper" on each side of the strap (e.g. 1/8" from the strap - it does not really matter where exactly, as long as you are not sewing through the strap or too close for it to move smoothly)
As before, if you don't want the stitches to show on the outside, take care to stitch the "stopper" to the felt lining  only.
Finish by folding down the "stopper" on each side and stitching it to the felt lining again.

Step 5.
Thread the strap through the "stopper".
Fold the "body" as before, with the felt lining outside.
Stitch on both sides.

Step 6.
Turn it inside out and check if it fits your phone.
If you used batting in Step 1 the cozy should be a tight fit. If it's a bit too tight you might want to trim the seam allowance down a bit.
Without batting it might be a bit loose, so if you decide you want it tighter just turn the cozy inside out again and stitch on both sides a bit further from the edges.

Step 7.
Almost there, we just need to tidy up the end of the strap and stitch on some velcro.
Depending on the length of your strap and your preferences you might want to trim the strap down or fold it under. 
E.g. you could fold the edge of the strap under about 1/4" and then again 1 1/4" and stitch it down.

Cut a piece of velcro to fit the end of the strap (don't make it too small, especially if your phone is one of the bigger ones).
Stitch the velcro to the end of the strap.

Put your phone into the cozy and check where you should place the second piece of velcro.
Mark the place and stitch the velcro on (by hand this time, I'm afraid -  at least I couldn't find a way to do it otherwise).

And here it is - your own almost magic phone cozy.

This is my first tutorial so it might be a bit "rough".
If you have any questions, if something is not clear or you've noticed a mistake, please leave me a comment.