How do you miter an inside corner on a quilt?

Baste the corner sections using ¼-inch seam allowance. This will stabilize the fabric. 

Make a snip through the top fabric, batting, and the backing fabric just to the basting line you just sewed.  

Make sure not to go past your threads.

Now you are ready to add the binding.

I made my own binding from 2 1/2 inch fabric strips. 

Fold the 2 1/2-inch strip in half with the wrong sides together. Press. 

Attach to the quilt top matching the raw edges. Sew on the edge using 1/4-inch seam allowance.

Miter the corners as you get to them.

Here is how to Miter an Inside Corner on a Quilt with the binding.

As you come to the first inside corner, continue stitching the binding to the cover top until you are about 1-inch from the center point of the corner, where you made your snip in the layers.

Next, carefully sew to the center of the corner where you snipped up to the threads.

It is time to make a straight edge for you to continue sewing. Lift up your presser food and leave your needle down.

Move the edge where you just sewed backward while holding the fabric to be sewed on yet steady.

When the fabric is straight and you have the raw edge of the binding lined up with the raw edge of the chair cover.

Lower the presser foot and carefully continue sewing.

The binding is sewn on the top side of the quilt. Turn the folded edge of the binding over the quilt edge and hand sew or machine sew on the back.

A Quilted Chair Cover with the Inside Corners Mitered using Handmade Binding.