My sister bought a new laptop for school recently and that gave me an opportunity to make her a laptop sleeve. I chose to go with worsted weight 100% cotton yarn, but I am sure it will turn out just as good with any other yarn too. 

I had some mint, white and grey yarn in my stash and decided to use these in a combination that wouldn't look too boring. 

The below pattern calls for a foundation chain in the multiples of 12 then add 3 chains. Using this calculation you can make a sleeve in pretty much any size. 

This pattern is free here but if you wish to buy an inexpensive printable PDF for this pattern you can buy it from my Etsy shop here.

Below is the pattern for a 14" laptop but will easily fit something slightly smaller or bigger.

Materials: 

Yarn: 100% cotton yarn in worsted weight

I used mill end nafs of 100% cotton from AC Moore.

Hook: 5.0 mm

Scissors

Tapestry needle

3 buttons about 1/2 inches in size

Note: all stitches are in US terms 

Abbreviations:

ch: chain

dc: double crochet

dc2t: double crochet two together

sc: single crochet

Chain 51 (12×4+3) with mint

Row1: dc in the 4th chain from hook, dc in the next 3 ch, *dc2t next 2 ch, dc2t next 2 ch, dc in next 3 ch, 2dc in each of next 2 ch, dc in next 3 ch*  repeat from * to * 2 more times. Then dc in next 3 stitches, work 2 dc in the last ch. (48) mint

Row2: ch3 turn, dc in the same stitch as ch3, dc in the next 3 stitches, *dc2t next 2 stitches, dc2t next 2 stitches, dc in next 3 stitches, 2dc in each of next 2 stitches, dc in the next 3 stitches* repeat from * to * 2 more times. Then dc in next 3 stitches and  end with 2dc in the last stitch. (48) mint

Row3: repeat row 2 with mint

Note: All subsequent rows are going to be a repeat of row2. Below I am only going to specify row number and color. The idea is to decrease the number of mint row repeats and increase the grey row repeats. Grey and mint are always separated by white. After 3 repeats start reversing the order.

Row4: mint

Row5: white

Row6: grey

Row7: white

Row8, 9, 10: mint 

Row11: white

Row12, 13: grey 

Row14: white

Row15, 16: mint

Row17: white 

Row18, 19, 20: grey

Row21: white

Row22: mint

Row23: white

Row24, 25, 26, 27: grey

Row28: white

Row29, 30: mint

Row31: white

Row32, 33, 34: grey 

Row35: white

Row36, 37, 38: mint

Row39: white

Row40, 41: grey

I stopped here. But if you want to make your flap longer follow the below sequence.

Row42: white

Here on repeat from Row1.

Edging: if you ended on a grey row continue with grey otherwise attach grey yarn to the corner where you ended your last row.

Row1: ch1 turn your work sideways and work sc evenly along the straight edge of the piece.

Row2: ch1, turn, sc all the way back along the same edge of the piece. Leave a very long tail for sewing. I left more than a yard long tail as I single crocheted the sides together.

Repeat Row1 and 2 of edging on the other straight edge. 

If you want to line the sleeve like I did, see lining section before continuing.

Now wrap the rectangle around your device and decide the position of the flap and how long you want it. Pin the sleeve sides, leaving a flap of desired length and with the tail, sc the sides together. Do this for both sides. Fasten of, hide the tail and turn your work inside out.

Sew on cute little buttons and we are all done!

Lining: 

I had some left over flannel fabric, it's actually a fat quarter, sew on the lining before you sc the sides.