This witch's dress is made from one of those ubiquitous black maxi skirts that are all the rage these days. All the materials for this dress were inexpensive and very little sewing is involved, so you will have a fabulous costume in no time and for little money.
Unfold the maxi skirt's top waistband. Lay it flat, right side up. Pin the top of the waist opening closed on the sides, leaving a 10" opening in the very center for the neck. Sew the top-sides closed. About 1" down from the top of the dress, cut out an 8" oval on the side seam for the arm opening. Repeat for other side. You could finish the seam by folding the raw edge towards the wrong side 1/4" and press then sew it using a zigzag stitch or double needle. Knit fabric does not fray, so do not worry about finishing the seam if unable to do so.
Clip a safety pin onto one edge of the ribbon and thread through the casing in the tulle. The ribbon should be at least 30" and no longer than 50". Once the ribbon is through to the other side, push the tulle together in the center, gathering it to make a skirt. The ribbon will be hanging out of the two sides of the skirt.
Wrap the ribbon around the maxi skirt dress and you have an adorable tulle skirt witch costume. Adjust the length of your skirt and dress as needed by cutting with scissors. Add felt shapes to the skirt of your witch costume by cutting out shapes and hand stitching on in various places.
Measure the circumference of your (or the wearer's) head and then add 1/2" to that measurement. Cut a piece of felt with the center circle opening the circumference measurement. Make the brim 4" to 6" wide.
Cut a rectangle of fabric that is the head circumference in width by your desired hat height (about 10” to 12” is good). Fold the fabric in half. On the folded rectangular piece, cut an arc, starting at the bottom fold arcing up towards the top outer corner. You should now have something that looks like a half circle.
With the center of the half circle straight edge coming to the point, wrap the bottom curved edge around to create a cone. Continue to adjust the cone shape until the bottom opening fits the center circle of your hat brim. Pin around the bottom cone edge. Hand stitch the side cone seam up towards the point or use a little felt fabric glue or hot glue (which works great on felt).
Place the bottom of the cone in the center of the hat brim. Pull the brim up and around the bottom of the cone and pin the bottom of the cone to the inner brim circle. Carefully sew the two pieces together.