These are so quick, and they are quicker still if you choose not to include the exterior pocket.
First, choose a piece of fabric to fold in half as the main body fabric and cut it to square it up (actually it is a rectangle, but you need to make the corners square). Then choose a pocket size and fabric, and cut the pocket and the straps. The straps will be about 14" by 2". Check your length by imagining holding the bag.
Press the edges of the pocket under on all four sides. Stitch the top hem. Pin it to one side of your main tote piece. Stitch it around the three unsewn sides.
Now fold up your bag and stitch the two sides together. Press the top hem under and stitch it.
To make the straps, which are 1" wide, press them inwards with the edges hidden inside. Then stitch up and down both sides. Next, pin and attach the straps to the bag using a box stitch in four places. Make sure the attachments across from each other are actually directly across from each other.