First, I cut 1" width strips of cardstock from 12"x12" pieces. Then I punched holes in both ends of each strip. If you don't want to waste the time to be sure that the holes match up EXACTLY, keep a blunt tapestry needle (yarn needle works GREAT here) handy to quickly thread the ribbon through the holes. This makes a pretty large pumpkin. For smaller pumpkins, adjust the length of the strips.
Next, I cut approximately 12" of ribbon. I used floppy ribbon here - but wired ribbon would be great for designing a vine for your pumpkins. Knot one of the the ribbon.
Thread the strips of cardstock wrong side facing up onto the knotted ribbon. If you are using multiple designs, be sure to alternate the strips as you thread them onto the ribbon. Use as many strips as you'll need to fill out the pumpkin. You'll notice in some of these examples, I only used a couple of strips to demonstrate the technique.
Punch a hole in your treat bag. Make sure your treat bag is no larger than half the length of your cardstock strips. Thread the ribbon through the treat bag. Now thread the ribbon through the other ends of the cardstock. Pull the the cardstock until you get a 'C' shape.
Arrange the strips evenly and add leaf embellishments. I like to separate the leaves by knots creating a vine. I just stamped my leaves in a copper ink and then embossed them with pale gold embossing powder; cut them out; and tied them onto the pumpkin using the ribbon already there. You could glue dot them on or whatever makes you happy! :) Trim ribbon.
In this finished example, I don't have the treat bag included, because this was a prototype. Your finished project could include the treat bags or not. I'm going to make them with treat bags in funky, bright halloween cardstock for Maddie's preschool class.
If you want to get real particular, you can either stamp the white side of each strip or buy two sided, colored cardstock as not to see the white insides. I used really cheap cardstock here. But the two sided (color on both sides) cardstock would work really well here.
You can do a rustic look with shredded edge cardstock that's been inked to look old and worn. You could add rafia to the top.
You could fill the inside with some moss, shredded burlap, or rafia that's been glued to the bottom inside of the pumpkin and let it peep through the spaces.
You could crinkle and ink cardstock strips before using them to make them look prim. (My fave)
You could use fabric scraps for the leaves.
You could cover thinner cardboard in fabric (use fabric glue) and have a sturdier, fabric pumpkin.