The trickiest Christmas knitting is going to be the striped toe socks. For one thing, the teenager who requested them is growing like a bamboo shoot. For another thing, and I'm confident you know this, FEET ARE WEIRD. They're oddly shaped. The toes are funky lengths, and nobody's are the same.
With that in mind, I forced the teenager to take off his socks and shoes to try on the in-progress socks while I traced his toes.
You do what you have to do.