4 Miter each bottom corner

Miter each bottom corner. Fold the bag so that, instead of coming together at a 90-degree angle, the bottom and side seam are stacked on top of one another (as in the image below). Then, sew across the corner, keeping the new seam perpendicular to the existing seams. Repeat this process on the other corner. When you flip the bag right-side-out, the corners will be blunted.