The linen fabric will be on the inside of your box. Consider a solid color for this. The cotton fabric will be on the outside. Consider a coordinating pattern for this. Use thin batting. If you can’t find any, iron fusible interfacing to the wrong side of your cotton fabric.
Pin the fabric and batting together with sewing pins first, if necessary. Be sure to remove the pins when you are done.
Use something long and slender, like a knitting needle, to push the corners out.
Be sure to tuck in the seams from the gap nicely. Use sewing pins to keep the gap closed, if necessary.
Use a thread color that matches your cotton, and a bobbin color that matches your linen. Consider using a contrasting thread and bobbin color. This will make the top stitching part of the design!
For a perfect cube, measure your fabric, and divide it by three. Draw a square in the center according to those measurements.
Remove the ink or chalk by gently wiping it with a damp cloth.
You can also glue the corners together with a drop of hot glue or fabric glue. If you use fabric glue, secure the corners with clothespins until the glue dries. You can match the embroidery thread to your fabric, or use a contrasting color for a hint of design.
Make sure that the two fabrics go well together. One of them will be your main fabric and the other will be your lining.
To ensure that each square is the same size, use a template cut out of thin cardboard. Discard the squares that you cut out, or save them for another project.
Repeat this step with the lining fabric.
Repeat with step with the lining.
Tuck the hem in at the gap neatly. Keep the opening shut with sewing pins if you need to.
Consider using a contrasting thread color for the top stitching. This will make it part of the design!
