The original pattern was written in Finnish. And Handimania posted a picture tutorial and some instructions on their website. (Update 2017: It looks like they have done a Google translate from the original Finnish since I originally translated this.) It took me most of a day, but I got it figured out.
I wrote the instructions down so that I could make them again and I'm sharing with you.
About 4 oz main color- WW yarn
About an ounce white- WW yarn
Large eye needle for weaving ends
Row 1- Ch 3, join to make a circle, ch2, 12dc in circle. Join with sl at to 1st dc.
Row 2- ch2, 2dc in each dc around (24) join
Row 3- ch2, (1dc in 1dc, 2dc in next) around. Join (36)
Row 4- ch2, dc in each dc. (36) cut white, join with main color.
Row 5-8- ch2, dc in each dc, join (36)
Row 9- ch3 (cts as dc), dc in 13 dc. Leave remaining unworked.
Row 10-20- ch3, dc in each dc. Finish off. Weave end.
Row 9- rejoin with last dc of tongue with a ch3, dc across to the other side, dc in am sp as ch 3 from tongue. (24)
Row 10-12- ch3 (cts as dc), dc in sm sp (increase), dc in each across, 2dc in last dc (increase).
Row 13- ch3, make increase, dc in 13dc, 2dc in next, dc in 14dc, increase in last dc.
Row 14- ch3, dc in each
Row 15-17- repeat rows 10-12.
Row 18- ch3, increase, (dc in 9dc, 2dc in next) 3 times, dc in 7dc, increase in last.
This is where you can customize the length. Try it on if you can. 22 rows gives you an 11-1/4" foot.
Row 19-22- ch3, dc in each dc.
Cut leaving a long end. Whip stitch your slipper end together.
Join with slip stitch in the base of the tongue where you join for the shoe- ch1, 2sc in each row end around, sl st to join join space on opposite side.
Ch1, turn, skip sl st, sc in each sc, join with sl st in sm sp as original join. Cut, weave in ends.
Row 1- Ch 3, 12dc in 3rd ch from hook, join
Row 2- ch3, 2dc in each. (24)
Row 3- ch1, (sc in 1dc, 2sc in next) around. Join. (36)
Embroider with black.
Ch 151, sc in 2nd ch from hook and each.
Weave in and out like shoelaces in the big holes left on the side where you put sc in row ends.