|First, you don't need to be a whiz in geometry. Think of this as a paper folding project, sort of like making snowflakes.
To help decide the size you want your fabric bowl, you can measure a favorite size bowl in your cupboard. Measure from one side to the other, going underneath the bowl. This is the diameter or width of the circle you'll need. A cereal size bowl will measure about 9". Also measure the top edge around, or circumference [of the bowl from your cupboard].
I used newspaper, but most any paper will work to make the pattern. It needs to be a little bigger than the width of the circle. Fold paper in half, then in half again, then each section in half again. It is now folded into eighths. Measure from center point out, half the diameter or width, and mark all of this eighth of paper. Cut along the marks, forming a circle. You could also trace around a plate or anything round that's the right size to make the circle [or use a compass], and then fold into eighths. These eighth markings are where you will draw in the dart shaped cutouts.
But first you'll want to make a small circle for the center of the bowl, so it will have a flat bottom. This should be at least 3" wide, but can vary depending on the shape of bowl you want. Center the small circle over the big circle and trace onto big circle. Your dart shaped cutouts will taper to nothing and stop at the small circle marking.
To determine size of dart shaped cutouts, measure outside edge of large circle, or do the math [diameter x 3.1416]. Subtract the top edge measurement you took, and that's how much needs to be removed in the dart shaped cutouts. Divide by 8, this is how wide each dart shape will start at the outside edge of the circle. This pattern has no seam allowances, the edges are butted together when sewn, so no need to think about those. Measure and mark each dart shape [or V shape] on each eighth of the pattern and cut out. A true V shape will give you a very cupped bowl. To make a less cup-shaped bowl, the dart shape will look more like a Y.
Now comes the fun part. You can preview what your bowl will look like, before cutting fabric or sewing. Take 16 little pieces of tape and butt/tape each dart together, one piece in the middle and one at the outside edge. If you like the shape, clip the tape apart and your pattern is ready to trace onto fabric. If you don't like the shape, retrace pattern and make adjustments.
To make a fluted edge, while pattern is folded in eighths, round the outside edge.
Instructions for sewing can be found online [see comments below]. I've used 3 layers of heavier interfacing to give the bowls a firm structure and it worked great. I've also used glue stick or spray glue to hold all the layers together while cutting and sewing [instead of fusibles], and they both worked great too.
These are really fun and easy to make! Any questions, feel free to leave me a message.