It's chain piecing.
See these are half of the triangle squares from the block. I have about ten hundred more of these to make, then press them, then sew them together into squares, then press, then sew those with the solid squares into blocks, then press, then sew the blocks into rows, press, rows into a quilt top, press then find a fabric for the bottom and quilt. That's all!
I also whipped this up today. Now there is some background here. Claire makes THESE awesome wrist pin cushions. I want all of them. Well I just need one, but I could never pick. I even had a dream that I had one and when I woke up and went to sew stabbed myself in the back of the wrist because I thought I had one! Then today clicking around I found THIS tutorial. These looked so easy I was sure I could do it!
I didn't even bother to read the directions again before sewing! Because I'm an idiot. (kidding mom, I know you don't like me to say that) I thought I was so clever, using a charm square for mine. Um... that makes a pin cushion about the size of a grapefruit! So I only had one charm of each of the fabrics, so I tried to flatten it out and just cut it to a smaller square. (It's already sewn to the strap at this point.) It worked... sorta. So mine is totally functional and I love it, but not nearly as nice as Planet June's. But alas, it works!
I also jammed a square of thick cardboard in mine before stuffing it so I don't stab myself. Again. I used my crop-a-dile to punch a hole in the center of the cardboard so I could still use the thread and button to make it have a little dip. (what's that called?)
So I love it! I plan to love the correct ones even more. Every sewer on my list, you might just get one of these!
ETA: AAAAKKK! Everyone look at your arms for me. Just the ladies. Are your arms hairy? That's everyone right? Because we are mamals. Tell me it's normal. I've never noticed all that hair before! No more pictures of my arm.