There are many reasons that you might want to make this type of food packaging. I have kids who often argue over snacks because they all like the same things, and sometimes there isn't enough of any one thing to go around, so we'll do a lucky-dip of snacks for road trips. These packages are also water resistant, and can be labeled with sharpie without it rubbing off, or soaking through to the food inside.
I use this for small packages of granola for topping yogurt, or for granola bars if I make my own. You may argue that sandwich, and snack bags are more convenient, but I'm sure you don't turn to instructables for reasons to not make stuff.
Step 1: You Will Need
1) Freezer paper. (Typically found in 18" widths on rolls)
2) Scissors. (the longer the better, within reason)
3) Shaping scissors, scalloped, or zig-zag (really optional, but it makes this a lot nicer)
4) An iron. (Capable of turning any steam function off)
5) Ironing board, or other safe surface for ironing.
Step 2: Cut & Fold the Paper
Cut the Freezer paper along the width at about 8" to get a piece 8" x 18".
Fold this in half lengthways with the shiny plastic sides facing inward, and press a seam along the open edge about 1/2" wide with a hot iron. This will create a permanent seal along the edge.
Try not to have the shiny plastic side of the paper touch the hot iron, so if your cut isn't very straight, you can overlap the edge so that the seam is covered on the underside by the top piece completely. The plastic won't stick permanently to an ironing board cover, but it will leave a mess on your iron.
It's pretty important to iron in a straight line, so if you need a straightedge I would suggest using one at this point. with a little practice, you'll be able to eyeball the seam pretty accurately.
Trim any excess from this sealed edge if you want it to look pretty.
Step 3: Cut Pouches Out, and Press Individual Pockets
From the tube that you have created, mark, and cut at 6", and 12" to create 3 smaller tubes.
fold the seam over on the pouch, and press it open so that the original fold line meets up with the seam on the back.
Press a new seal into one end of the new sleeve to create a pouch.
Step 4: Make Bunches of Pouches, and Fill Them.
These pouches can be made in different sizes, for nuts, or pretzels. I have some narrow tubes here that were made for granola toppers for my yogurt, and some bigger ones that I made for some pumpernickel-breadstick granola bars.
Once you have made enough for what you're packaging, fill those suckers up. Leave at least an inch at the end of the pouch where you'll need to seal it. If you make something smaller, you can seal as much as you need to at the end to accommodate a tighter fit.
Step 5: Trim the Sealed Edges at the Ends
This is where you'll use the shaping scissors. Trim the very edge of your pouch with the shapers. Zig-zags are better here, but if you're using scalloped scissors, make sure that the points on the shapes are facing inward as they're used to make opening the package easier.
If you're not using shaping scissors, then cut a "V" notch into the sealed end where you'll be able to tear into the pouch.
This is now done, and can be labeled with stickers, or sharpie, or left plain for a lucky-dip.