Cut the fleece fabric to the dimensions desired. For example, if an 8-inch by 8-inch bag is desired, cut an 18-inch by 9-inch piece of fabric.
Fold the fabric in half length-wise and place it folded onto a surface. Cut a 3-inch square in the center of the fabric.
Cut a 6-inch square of clear vinyl. Lay the vinyl on the wrong side of the square hole. Pin the vinyl to the fabric several inches away from the intended sewing line.
Stitch around window opening, sewing the vinyl and fabric together. Trim the vinyl seam allowance to 1/2 inch outside the seam.
Place the right sides of the fabric together. Take the ribbon, fold it in half and place it in between the two layers of fabric along the bottom edge of the bag so that the raw edges of the ribbon are even with the raw edges of the fabric. Sew around the edges and leave a 3-inch opening at the top to enable turning. Turn the fabric right side out. You now have an empty I Spy bag with an opening and a ribbon length extending out from the bottom seam for attaching the I Spy label.
Select approximately 50 novelty items and buttons to place inside the I Spy bag. Place the items inside the bag. Make note of the items you place in the bag.
Place a funnel into the opening and pour the poly pellets into the bag. Fill the bag so that it is full, yet the items can be moved and shifted around within the bag. Top stitch around all the edges to finish the bag and close the opening.
Make a list of most of the items placed in the bag. It isn't necessary to list all of the items; however, most of them should be listed to assist in finding them. Enter the list into a word processing program, print it out onto card stock and consider covering it with contact paper.