I generally just use a back ward loop to increase at the beginning and end of a row like this. Sometimes it is easier to disguise when you knit the first stitch and increase on stitch 2, and then increase just before your last stitch. Most of the time, a backward loop doesn't leave a trace, though. You could use a knitted cast on or cable cast on, I think, though I haven't mastered either of these cast ons yet.
Learning how not to leave marks takes some time and patience.
GL and keep trying.
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blanket for a man, scarf, poncho, 1 rug, baby blanket, finger puppet
finger puppets: cat (2), dog, pig, frog, butterfly, bunny