Remove the handles from the bag. If the paper bag comes with handles, carefully remove them from the top of the bag. Most likely they have only been glued on and should come off fairly easily if some care is taken. Set aside the handles for later.
Cut out one of the narrower sides of the bag, starting at the top. Then cut out the bottom panel. Reserve the side panel if you need to make handles for the portfolio. Fold the remaining bag in half at the existing crease.
Attach the handles to the portfolio. If the bag came with handles, attach one handle to the center of each side opposite the fold with the stapler. If you need to make handles, cut two strips off the reserved side panel that are 2 inches wide and about 8 inches long each. Fold the strips in half lengthwise and staple together. Attach as previously instructed to the opening of the portfolio.
Allow your child to decorate the portfolio with the crayons or markers. If using markers or especially if using paints, let the portfolio dry completely.
Cover the portfolio in self-adhesive laminating sheets. Trim off any excess around the edges. This will provide strength and durability.