We thought we answered this question years ago. Apparently we did not.
There is a hard, unsatisfactory way to skin hazelnuts, and then there is a new, scientific way to skin them. You might not call either of them easy, but if you've ever tried the hard, unsatisfactory method, you will love the new one. Either method also produces toasted hazelnuts, which are a lovely thing.
The traditional method involves roasting the hazelnuts on a baking sheet in the oven at 350°F (175°C) for 10 to 12 minutes, shaking the pan once or twice during the roasting. Pour the nuts into a clean towel, grab the corners to bundle it up, and rub the nuts vigorously against each other inside the towel for quite a while, until most of the skin comes off. All of it will not come off, but you can get them fairly clean.
The second method involves boiling the hazelnuts in a quart of water with four tablespoons of baking soda for three or four minutes. Rinse them in a colander under cold water. Some skins will pop right off; others will require you to slip them off; and some will take a little rubbing. But at least the whole skin will come off.
Pat the nuts dry, then roast them in the oven at 350°F until they are lightly browned. In our experience, that can take anywhere from 10 to 20 minutes, depending on how much water the nuts absorbed.
It is our belief that once you use the second method of skinning hazelnuts - with all its mess and fuss - you will not go back to the first method and its badly skinned nuts.