Step 1: Tools, Materials, & Prep
To construct the bag, only the basics are needed: sewing machine (or needle and thread), scissors, pins. Chalk for marking the pattern is useful but you can do this with just pins, or draw the pattern on newspaper.
The first thing to do is determine how long a strap is needed, by measuring around yourself from shoulder to opposite hip. Hold the tape together at a comfortable length, and make sure you can get the loop thus formed over your head. This measurement is the minimum length of the strap plus the bag opening. Mine was about 40".
Step 2: Cut Out the Pattern Shapes
I drew the pattern directly on the fabric but you can use newspaper if you prefer. The spoon shape I drew by eye, and the rectangle by measuring: the width as noted above, and the length by measuring around the head of the spoon.
My measurements were:
spoon handle = half the strap length: 14"
spoon head = rectangle length: 27"
rectangle width = 40 - (14 + 14) = 12"
Also, cut one or two pocket-y shapes from the lining fabric, as well as some flaps to cover the velcro closure -- more on this in a bit. Remember about seam allowances when cutting the pocket pieces out. This isn't as vital for the rest of the pieces as they're bigger and pretty well mungeable.
Step 3: Pockets
Fold the edges of the pocket down and press them. Pin in place on the side piece, about two inches or so from the edge that will be the top edge of the bag. Stretch the elastic when you pin so the pocket would lay flat, if there were no elastic. This is a little tricky and may require a third hand, or knee, to hold one pinned end while you use two hands to pin the other. Topstitch!
And repeat for the other pocket on the other side (unless you only want one pocket, a perfectly valid design decision).
Step 4: Velcro Closure
Stitch the velcro pieces a little ways above the pockets. Make a flap by cutting a rectangle an inch or so wider than the velcro pieces are long, and long enough to fold over a few times -- I just cut it Long Enough and trimmed it later on. Stitch the third velcro piece (loop) across the middle of the flap piece, then fold the flap over top of the velcro and stitch down each side. Turn the pocket you just made right side out, so the velcro is accessible again. Pin the flap in place over the hook side, open it out, and stitch it down. Trim the excess and topstitch to cover the raw edges.
Step 5: Construct Bag
Lay out the side piece rectangles and mark the centers of each edge with a pin. These will be the bottom of the bag. Take one of the spoon pieces and fold it lengthwise to find the center of the spoon head. Being careful to place the right sides together, pin that center point to one of the bag side center points. Continue to pin the two pieces together around the sides until you get to the end of the side piece. This ought to be about where the spoon shape narrows to the handle.
Stitch both pieces together in this manner. Finally, sew the two spoon handle ends together to join the strap. Repeat for the body fabric.
Step 6: Attach Shell and Lining
Now I could diverge into topology and the strange ways of turning things inside out through holes in their sides, but it's easier to just say, stuff the strap down in between the lining and the shell, and pin just the side edge, so the strap appears to be caught underneath. You'll have two holes, one on each side, where the straps are. Don't make these too small as you'll have to stuff the wadded up bag through one of them when you turn it. Stitch the pinned edge together. Almost done!
Do the turning, now. The first bit is easy as it consists of the strap, which you can grab through one of the side holes left by the straps. Keep pulling and the rest of the bag will start to come through the hole, and you may have to squeeze it some. It will become unrecognizable and octopus-like but persevere. Eventually you'll have everything turned out, with the lining laying like a herniated stomach ... stuff it inside the bag quick, that's not a fun image!
Step 7: Finishing
Fold the end of the ribbon up, cover the strap and pin starting at the bag edge. Pin all the way around, and when you get to the other end, trim the ribbon to size, leaving enough to turn up inside on that end as well. Stitch. Fill with yarn or books or beads or electronics components or tassels or whatever project you want to keep with you to work on.