I just made this simple cell phone cover for my new flip phone. I'm calling it "Streamline." Rather than having a button closure to keep the phone in, I've hooked the top edge over the antenna to keep it on the phone. I just inserted a 3-stitch buttonhole for the antenna to fit through. Easy! (Well, buttonholes are a bit tricky, but you can do it!)
Top view, and back view
Yarn: Adrienne Vittadini "Martina," merino/silk blend, color 403. This yarn was mucho dinero; it had a sheen that was hard to resist. If I were to do it over, I'd consider KnitPick's Wool of the Andes "Mist", or just use some scrap yarn, or whatever I fell in love with at my LYS. If the yarn knits up at 4-5 sts./inch, it can be used at this gauge. If it's a very different guage, you'll need to change the number of stitches in the buttonhole: BO 3/4" of stitches, or more if you have a very thick antenna.
Needles: size 7, or size to get gauge
Gauge: 4 sts/ inch (or whatever you get with the yarn you love)
CO 14 stitches (or your gauge, multiplied by half the circumference of phone, plus 2 stitches)
Knit until work is twice as long as cell phone is tall.
Beginning of next knit row: k2, make a 3-stitch One Row Buttonhole (see below), knit to end of row. Use Basic Purl BO to BO all stitches. Fold in half so CO & BO edges meet. Seam up the sides with mattress stitch. Viola!
Buttonhole instructions (accompanying videos here, scroll down):
Step 1 -- Bring yarn to front; slip 1 purl-wise, bring yarn to back.
Step 2 -- Slip 1 purl-wise, pass first slipped stitch over second. (repeat this part 2 more times--passing over 3 stitches total, for a 3-stitch buttonhole) Place last stitch back on left needle. Turn work.
Step 3 -- Cast on 4 stitches using the cable cast-on method.
Step 4 -- Turn work (so RS is facing). Bring yarn to back; slip first stitch of left needle onto right needle and pass last CO st over it. ....You're done!