As I mention in this post, I tend to buy slightly larger butternuts than usual, and always look for ones with the longest straightest shafts. I’ll then cut it in half lengthwise, right above the bulb that contains the seeds. I’ll save this part for another use since it’s less uniformly shaped and annoying to peel. Usually, I roast it in the oven and then scoop out the flesh for a puree or soup. With the remaining cylinder, I cut the top off, so I have two perfectly flat sides to work from. Then I stand it on the cutting board and shave the skin off with my chef’s knife. This is WAY easier than using a peeler and trying to hold onto that slippery squash. You can then create thin planks, followed by matchsticks. Viola!
If you soak the butternut squash matchsticks in cold water for 30 minutes, drain and pat dry, you'll get an ever crispier fry!