*prepare the bag: carefully remove the handles, & toss them into your recycling bin. next you'll need to cut the bag open; do this by cutting down one corner seam, then around the base. now your bag should lie flat.
* place your item on the bag, & measure 2 inches around. you can either cut out 2 of of this size, or fold your bag over, then cut once. i did the latter here. definitely fold if your item is bulky.
*with your machine set to zig zag, stitch around three sides. leave a bit of a seam allowance, & don't forget to back stitch.
*slip your item in. make sure you ease it to the bottom of your envelope, so you don't accidentally sew through it. for a bit of padding you can first wrap your item in some of the tissue you saved from your birthday prezzies.
*sew the fourth side closed, back stitching once more to avoid ravelling.
*if your bag has a fancy design, as does mine, add a label for the address.