I love Bag Stitch!

Taken from a sampler I made earlier this year, here is a pouch I made using Bag Stitch

This is a sc/ch fabric where you sc into the sc of the row before last, enclosing the ch of the previous row.  You never sc into a ch, always into the sc of the row before last, always enclosing the ch. The chain stitch keeps the single crochet from stretching out of shape.

Blue and Red Bag Stitch pouch
Historically - to the extent that anything in crochet is historical - the most common way to make a basket or pouch is to work VERY TIGHTLY in single crochet, which can hurt your hand.  By switching to this pattern stitch, you can save your hand from the pain of working in such a tight gauge (to make a sturdy fabric), bump up the hook size to something reasonable, and still end up with a sturdy bag fabric that does not need to be lined (unless you really want to). As an example, the Blue and Red pouch is a recent project.  I used a double strand of #10 cotton and a size D/3.25mm hook, and started with a base chain of 50 stitches.  This is worked in the round, but the stitch works well in rows, too. Using more than one color gives the added bonus of a faux Fair Isle effect when switching yarn color from one row to the next.  Reading at the pouch from the bottom up, there was:
  • (2 rounds blue, 2 rounds red) 3 times, then 
  • 3 rounds blue, then 
  • (3 rounds, 1 round, 3 rounds) of red/blue, then blue/red, then red/blue in the middle, then
  • mirroring the beginning pattern of 2 rounds of each color, and
  • Bag Stitch Pouch with closure
  • topping off the pouch with alternating rounds of blue and red -- which ends up making vertical stripes.

That is a nice bit of color work, with each round using only one color - remarkably brainless for as fancy as it looks.  You can see the round beginning/end jog especially well in the top bit.

Once the flat envelope pouch was done, I added a zipper going in the opposite direction, added I-cord loop at the bottom of the zipper (top of the photo), and another I-cord at the top of the zipper, joined to the zipper pull (left side of the photo).  When the pouch is zipped closed, the long I-cord strand folds to slip through the smaller I-cord loop to cinch up the top and make a handle/strap -- a fairly classic pouch shape.  And there was nothing in the bag to make it hold its shape in this picture.

Here is a diagram of the stitch in rows.  Starting at the bottom left corner, the diagram shows a starting row of ch10, sc in 4th ch from hook.   Note the ch-2 turning chain for each row.

It can be tricky to see the chain stitches in round 2 when you want to sc into the skipped foundation chain.  It is possible to start with a foundation row of (sc, ch1), but that needs thinking, too:  The sample picture below shows 12 patt sts across, then rotated, continued along the bottom back to the start (12 more patt sts), rotated again to continue in a coil, and making 7 patt sts in the new row working into the 'skipped ch' (which looks a lot like the body of a dc lying sideways in foundation stitch).
Sample of foundation bag stitch

Until you get the hang of seeing your stitches, it is easiest to start the pattern with a full row of single crochet.