Line a 9-inch loaf pan with parchment paper or wax paper.

In a medium bowl, stir together the peanut butter, brown sugar substitute, and water until blended and smooth.

Add the coconut flour, stirring until blended. The mixture should be very thick, but not dry. If it appears dry, add a few more teaspoons of water until no longer dry. The bars will be very firm once chilled.

Press mixture evenly into prepared pan. Firmly tamp down, smoothing the top. Refrigerate for at least 2 hours until firm set.

Use paper lining to remove bars. Cut into squares.