In a large bowl, sift together flour and salt. Add cold butter, and rub flour and butter between your fingers. Make a well in center of flour mixture; pour in some cold water, mixing until you have a firm, rough dough, adding additional water if needed. Cover and refrigerate for about 20 minutes.
Turn out dough onto a lightly floured surface; knead gently. Roll dough into an 18x12-inch rectangle. Fold dough into thirds, like a letter. Turn dough 90 degrees. Roll dough into an 18x12-inch rectangle again. Fold dough into thirds, like a letter, again. Divide dough in half, and wrap in plastic wrap. Refrigerate for at least 20 minutes.
Recipe by Bake from Scratch at https://www.bakefromscratch.com/russian-salmon-hand-pies/