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This bag is an excellent project for a beginner. If you haven't already reviewed our excellent wikiHow on Crochet, be sure to check it out (along with the helpful accompanying video instructions). For this project, you only need to know how to do the chain stitch (usually abbreviated “ch”) and a single crochet (usually abbreviated “sc”). This is a flexible pattern, and you can adapt it to make small envelope style clutches or even laptop or tablet sleeves. If you're planning on carting a particular item in your new bag, measure it in advance (e.g., your laptop) or measure a similar style bag so that you have the basic dimensions and shape in mind. Keep in mind, yarn "stretches"! If this is one of your first crocheting projects, it will probably be best to stick with a simple, plain yarn of cotton or soft acrylic. Cotton yarn "stretches" less than acrylic. Ask the yarn shop manager for help if you're not sure what to use. You may also want to choose a solid color yarn so that you can see how the stitches are made and count them more easily. Most yarn labels indicate what size hook you should use; it will be best if you stick with the recommended hook size.  As a general rule, the thicker the hook, the thicker the yarn will need to be. If you want to complete your project faster, choose a thicker yarn and hook. The stitches will be larger, and you'll build up rows faster. Larger stitches do "stretch" more than smaller stitches, so take this into account. As with any project, creating a test swatch is a good idea. You may be impatient to get started right away on your bag, but taking the time to make a small square (approximately 4"X4") can save you time in the long-run. Making a test swatch can help you gauge (determine) your tension (how loose or tight your stitches are) and figure out how many stitches you will have in one inch. Because this is a beginner piece, you will be creating either a rectangle or a square (the top and bottom of your bag will be equal lengths, as will the sides).  More advanced projects will allow you to create different shapes, such as an isosceles trapezoid where the top tapers in. You'll need to learn how to decrease stitches to be able to make this shape. For small to medium size bags, between 30 and 60 stitches should work well. Be sure to remember how many stitches you included in this initial, beginning chain. You will want to write it down, and if your chain is particularly long, you will want to use markers every ten to twenty stitches to help you keep count. Continue making single crochet stitches back along your chain. Now count your stitches! You will find that you have one less single crochet stitch than you had of chain stitches. This is good! It means you placed your hook in the correct loop when you made the 1st single crochet stitch of the row. (Example: If you want your bag to be 40 single crochet stitches across, you need to make an initial beginning chain of 41 stitches.) Once you've completed your initial beginning chain, which will be as long as you want the width of your bag to be, you'll need to turn so that you can start the next row on the opposite side. You will need to do this every time you get to the end of a row. To turn your work, simply rotate clockwise, (as if turning a page in a book), so that your last stitch in the current row becomes the first stitch in the new row you are starting. Chain 1 stitch, then turn your work as described above. Continue, row after row, up to the height you want your bag to be.  You will be folding up the bottom part of the bag (the top will fold down as a flap). Keep this in mind as you crochet up. Don't make your piece too short. If you want your bag to be 12" high (when the flap is folded over) with a 6" flap, you'll want to crochet your piece to be 30" tall. Once your piece is as tall as you want it to be, you need to fasten off the yarn. Fastening off when crocheting is actually quite easy. Simply cut off your yarn from the skein of yarn, leaving a tail of at least 6 inches (15.2 cm). Pull the tail of yarn on your hook all the way through the last loop of the last stitch. Pull on the yarn to tighten it. Then, using a "yarn needle", weave the tail through the stitches in your top row. . Fold up the bottom half of your bag until it is as deep as you want your bag to be.  Check to see if there is a “wrong” side to your piece of crochet fabric; if you prefer the look of one side, make sure that side is facing out as you fold up. Using a matching color yarn (most likely the same yarn you crocheted with, unless you like the look of a contrasting colored seam). To sew the side seams together, start at the fold and use what is called "a whip-stitch" to make the seam. Stop at the point where you want the flap to fold over.
Review the basics. Decide what kind of bag you want. Choose your yarn. Choose your crochet hook. Make a test swatch. Chain the amount of stitches you want the bottom and top width of your bag to be. Turn your work, then single crochet in the 2nd chain from the hook. Continue to single crochet to the end of the row. Fasten off your yarn. Fold and sew to make your bag.