When I'm working in the rounds, I join my yarn in the top of the first stitch, NOT the chain. To begin the next round, I chain the required amount and place my first crochet stitch in the same stitch I joined the yarn from the previous round. This creates an invisible join. HOWEVER.... when working with HDC, your seam will not be straight. It will slant. By repeating wounds 8 and 9 in the pattern for the cozy, it will give your work a straighter seem. If you're working with variegated yarn, see my tips below the pattern.
Joining a new color -- I'm sharing with you a new trick I picked up to join a new color yarn when working in the round. Before joining your yarn at the end of a round, pick up the new color and pull a loop through the loop of the old color already on your hook. Then join the new color to the first stitch to close up the round. I have noticed that this makes a cleaner looking color change in my work.
Supplies & Terms
Worsted yarn - 2 colors (MC: main color, TC: tail color)
Sc - Single Crochet
Hdc - Half-Double Crochet
BLO - Back Loop Only
FLO - Front Loop Only
Round 1: 6 sc into MR, join
*Alternately, you can chain 2, 6 sc into the second chain from the hook and join to the first sc
Round 2: Ch. 1, 2hdc in ea stitch, join - 12
Round 3: Ch. 1, (2sc, sc) around, join - 18
Round 4: Ch. 1, (hdc, hdc, 2hdc) around, join - 24
Round 5: Ch. 1, (sc, sc, sc, 2sc) around, join - 30
Round 6; Ch. 1, working in BLO, hdc around, join
Round 7: Ch. 1, hdc around
Round 8: Ch. 1, hdc in the 2nd stitch, hdc to end placing 2hdc in the last stitch (30)
Round 9; Ch. 1, hdc around
Repeat rounds 8 and 9 three more times for a total of 15 rounds
Switch to TC, join
Round 16: Ch. 1, sc around, join - 30
Round 17: This round will be worked in the front loops only. In 2nd stitch, 5hdc, sl st in the next, repeat around, ending w/ 5hdc in last stitch, join, FO
Row 1: Starting in 2nd ch from hook, sc in next 10 stitches, 3 sc in next, sc in last 10, turn (23)
*This will be the wrong side of your tail
Row 2: Ch. 1, in BLO, sc dec, sc next 9, 3sc in next, sc next 9, dec in last (23)
Row 3: Ch. 1, in FLO, sc dec, sc next 9, 3sc in next, sc next 9, dec in last (23)
Repeat rows 2 and 3 one more time. Fasten off
With the wrong side of the tail facing you, join TC yarn in bottom right corner of the tail (last chain stitch from row 1), ch. 1, sc in same
Sc evenly up row edges, sc in FLO across top, sc evenly down row edges on other side, Fasten off.
Attach tail between rounds 6 and 7 of cozy
I love how variegated yarn creates stripes and thought it looked cute on these cozies. But after making a few, I realized a few things need changed to accommodate this kind of yarn. If working with variegated yarn, work in continuous rounds from round 7 on to prevent your colors from lining up all wonky. Stripes that don't line up drive me crazy!!
Since you won't be joining rounds with this yarn, it can be kind of tricky to keep track of where a rows ends and the next one begins. A running stitch marker is great for this! To do this, take a piece of yarn that is a different color than your cozy. A thinner yarn works best. Drape the yarn over your work after the last stitch in round 6. Work round 7 and before moving to the next round, bring your yarn from the back to the front. Keep doing this at the end of each round. When your done, just pull out the yarn!