Here's the bag that started out a flat 5" x 8-1/4", and became a 3" x 2" x 7" gusseted bag. The stamp is from this year's Ronald McDonald House stamp set "Tag It" (wood mounted item #130300 $22.95/cling mount item #130303 $16.95) $3 from the sale of each stamp set goes to the Ronald McDonald House Charities.
It's recommended to use the Simply Scored tool to make the score lines, but the Stampin' Trimmer also has a scoring blade, the Simply Scored just makes a softer, deeper score.
After scoring, trim just a hair off the bottom to open the bottom of the bag.
Pre-fold along the score lines ....
Fold in the short sides first, then close up with the long sides. I used SNAIL adhesive to secure mine, the Tag a Bag accessory kit also comes with Smoky Slate tape to secure the bags decoratively. You can add a cut piece of chipboard from the kit to the inside bottom to stabilize the bag, just a little smaller than 2" x 3".
Tag a Bag Gift Bags: (item #131370 $3.95 for 10)
Tag a Bag Accessory Kit (item #130153 $7.95 for 10 large tags, 10 medium tags, 10 mini clothespins, 3 colors of baker's twine -20' ea-, 40 Stampin' Dimensionals, 5" of Smoky Slate self-adhesive strips)
Related items - Tag a Bag Gift Boxes: (item #130927 $6.95 for 8 Kraft food safe boxes with acetate sleeves, 6-7/8" x 2-1/8" x 2-1/2")