This is a popular sock design among the Finnish knitting community. Detailed instructions available in Finnish but there are example pattern charts available which of course are universal. Jonsukat is more like a sock recipe than a detailed pattern. Each pair of Jonsukat is unique, but they do have some common characteristics

• “Faux cable” ribbing, effect color
• Two-color high contrast (e.g. black and white) stranded colorwork with simple patterns that do not have more than 3-4 sts per color, so no long stands of yarn to worry about in the back. These patterns can be improvised
• One section in the leg is with a effect color
• Heel with effect color
• The leg part is 2 row stripes with the high contrast colors
• Replace the second to last stripe of the lighter color with the effect color
• Toe in effect color

Improvising is allowed and encouraged. The Facebook group contains variations, such as an ankle version of this design, as well as other patterns from the same designer.