This guide to shaping bag bottoms was written by Christine Down.
Boxed Corners – Type 1
This type of boxed corner works best with a pattern that has a regular oblong front and back for the main bag pieces. These bags are sometimes called “Basket-style bags”
These bags come in a variety of sizes. (The front and the back are oblongs.) They have differing closures from a magnetic snap to flaps and zips. This was the first type of bag I made and it is an easy pattern.
Cut out your bag and prepare the front and back bag body pieces by adding your chosen interfacing. Place the body pieces right sides together and stitch across the bottom and along both sides. Work out how deep you want your bag to be. (The distance from the front of the bag to the back) Fold the bottom corners flat matching up the centre bottom seam with the centre side seam. I say fold, but really you need to squish the corners flat!
Measure half the depth distance from the corner along the seam line and mark. For example, if you want your bag to be 20cm deep measure 10cm from the corner.
Draw a straight line at this mark across the corner. Double stitch along the line. Trim. Turn the bag the right side out. This method is the same regardless of how deep you want your bag to be. Just adjust the measurements. You do the same with the lining so it will nest snugly inside your bag.
Boxed Corners – Type 2
An alternative to the previous corners is to cut the corners first. Measure a square at each corner, the straight lines must be the same length, i.e. half the length of the width of your bag. So, if you wanted your bag to be approximately 20 cm deep (front to back measurement) the straight lines you cut should be approximately 10cm each. Cut out the squares and sew down the side seams and across the bottom.
Push the corner raw edges together. The side seam should be on top of the bottom seam (see picture). Stitch across the corner. Repeat for the lining but leave a gap in the bottom seam for turning out.
Another method for a boxy corner is to use a gusset, but the gusset will follow the shape of the bag front and back so it is suitable for curved bags as well. The gusset is the strip of fabric that joins the bag back to the bag front. Once you’ve cut out your bag pieces and added your interfacing, pin the gusset (or use clips) to the bag front. If it is a rectangular shape you will need to snip the gusset at the corners. Only snip as far as the stitching line.
This will allow you to turn the gusset around the corner and lie it parallel to the sides. Stitch the gusset to the bag front. Then pin or clip the bag back to the gusset. Clip as before and stitch into place. Curved gussets are sewn the same way.
You can make a curved bag bottom by adding darts to the bottom seams. This is made the same way as darts in a dress pattern. Cut out your bag, cutting around the dart shape. Prepare the bag fabric with your interfacing. Match up the two sides of the dart and stitch. Do the front and back pieces and then place them right sides together and stitch around the bag body. Like nearly all bag patterns you will cut the lining fabric to match and sew it in the same way. That way the lining will fit into the bag body comfortably.