I made these teeny box pouches a few weeks ago using this tutorial from experimentalk.  Easy peasy. I used up a few leftover pieces of fabric, quilted them directly onto some batting using the quilt-as-you-go method, and then added a bit of lining fabric afterwards that matched the size (about 8 inches by 12 inches each). 

The resultant pouch is quite small, but is ideal for all the bits and pieces that are jiggling about loose in the bottom of your bag. Each pouch here fits in a large wad of cotton wool pads and a tube of baby bum cream. You could make the boxed corners flatter and make a cellphone pouch, or a pencil case, or a coin purse...

No separate lining required? My kind of quick project! I overlocked the edges together, and zip zip zipped along the edges to make a boxy pouch about two inches tall. I also used fray-stoppa on the exposed overlocked edges on the inside to stop any unravelling, but really, you hardly even see the stitching and it saves about twenty minutes of fussing with a lining and turning inside out and pressing and whatnot so I'm rather pleased with that.