Position a rack in the center of the oven and heat to 350 F.

Line an 8 1/2-by-4 1/2 or 9-by-5-inch loaf pan with parchment paper, leaving an overhang for lifting the bread out later.

Heat the butter in a small skillet or saucepan over medium heat. Add the garlic and red pepper flakes, if using, and cook for 1 minute.

Remove the pan from the heat and add the parsley.

Peel apart or slice a biscuit in half horizontally to make 2 thin biscuits. Brush the cut side of each one with the butter mixture and then stack the second one on it and brush that one. Repeat with the remaining biscuits, stacking them on top of each other. Place the stacked filled biscuits in the pan sideways to form the loaf—you might have to do this in a few batches—ending the loaf with the uncut, ungarnished side of a biscuit. If you have any butter mixture left, brush it over the loaf.

Bake the loaf for 35 to 45 minutes, checking it after about 25 to 30 minutes. If necessary, cover it loosely with a sheet of foil to prevent over-browning. Test the loaf with an instant-read thermometer. It is done when it reaches 190 F in the center of the loaf.

Let the loaf cool for about 10 minutes in the pan on a rack and serve warm.