On a lightly floured surface, working with one piece of dough at a time and keeping the rest covered, roll each piece into a 20-inch rope, about 1/2 inch thick. Cut rope into 1-inch lengths. Using your thumb, roll each piece of dough over the back of the tines of a floured fork, leaving an indention from your thumb on one side and the markings from the fork on the other. Place gnocchi on prepared baking sheet. Repeat with remaining dough. (Make ahead: Cover and refrigerate for up to 1 day, or freeze in an airtight container for up to 1 month.)