Normally when creating string quilts, I let the corners happen organically. When a triangle fills a corner, it's sewn on and that section is complete.
With this yellow and M&M top (what should I call this, anyway?), however, I wanted the corners to be fairly similar in size, which meant
*gasp*
planning!
For the first few blocks I used my usual ham-handed method of laying the triangle face up in the corner, carefully turning it face down along the long edge, then scooching the triangle a 1/2" back toward the corner again before sewing it down and hoping for the best. There had to be a quicker way, one with less trial and error.
Bonnie Hunter's Essential Triangle Tool to the rescue! I wasn't very scientific about this: I looked through the corners I had completed so far and found a couple I was happiest with, flipped the corner piece back so I could see the seam, then lined up the ETT with the hypotenuse so I could figure out what line would give me that result again (I really wish now I had taken pictures of what I just tried to describe.) In this project, the scant 1-1/4" spot (using the red lines) fit the bill. Square up the ruler to the raw foundation corner
and the bottom edge is where the triangle hypotenuse goes (these measurements assume the standard 1/4" seam and all dog-ears intact. Again I say:
this project.)