Crocheted hats come in many varieties, from lacy cloches to cozy beanies. If you want to crochet a hat with ear flaps, you simply crochet it like a traditional beanie and then add the ear flaps as an addition. Crochet your ear-flap hat in worsted-weight yarn with a size H hook for a warm, snug style.
Start with a circle. Make two chain stitches and five single crochet stitches into the second chain from the hook. Join with a slip stitch to form a circle. Increase your circle for the next few rounds; for round two, make two single crochets in every stitch around for a total of 10 stitches. For round three, make one single crochet followed by two single crochets around for a total of 15 stitches. Continue to increase in this manner until you have the circumference you want for your hat (it should measure a few centimeters smaller than the circumference of the wearer's head).
Single crochet in every stitch around and join with a slip stitch at the end for all subsequent rounds. This will form the height of your crocheted hat. Continue to crochet until the hat is tall enough to cover the wearer's head and begin to come down onto the ears.
Fasten off your work and reattach the yarn with a slip stitch on the side of the hat. Join the yarn at the point where you want the back of one ear flap to be; make approximately 10 single crochet stitches around the brim of the hat, and then chain one and turn. Work three more even rows, then decrease the following row. To do this, make a single crochet two together stitch in the first and last stitches of the row. Make one more decrease row and then one more evenly crocheted row and fasten off. One ear flap is complete; repeat this process on the opposite side of the hat for the other ear flap.
Join a new length of yarn on the back of the hat near the seam. You can use the same color you have used for the rest of the hat, or use a contrasting or coordinating color for a more colorful option. Make a single crochet stitch in every stitch around the hat until you come to the ear flap; then single crochet around the edge of the ear flap and back up to the hat brim. Continue to single crochet around the front of the hat and around the other ear flap and the other side of the hat until you come to the place you started. Join with a slip stitch and fasten off. Weave in your ends with a large-eye blunt needle and your hat is ready to wear.
To add an under-chin tie to your hat, attach your yarn at the bottom tip of the ear flap. Make a length of chain stitches that is long enough to tie the hat around the wearer's chin halfway, and fasten off. Repeat on the other chin flap and use these chain lengths to be the ties for the hat.