It's a triangle block called Tennessee Valley. It's located on the right side, 1st position (RS1). I've completed the block for the black background quilt. It looks like this:
This block is sewn using foundation paper piecing, a technique I learned in this class. This is a terrific technique, but it does have its own set of skills to master in order to get perfect blocks. This block has 3 sections. The challenge with this block is to get the stripes to match at the center seam, where two sections are joined. Notice in the picture below that the order for sewing the background and the colored fabric alternates for each section; one begins with 1 at the bottom and the other begins with 1 at the top. This results in seams that lie in opposing directions on the back, which allows you to "nest" the seams together when sewing the two sections together, which I'll show in a subsequent post.
For me, it's best if I arrange the cut pieces according to the paper pattern, otherwise it's so easy to pick up the wrong piece if they are just stacked up according to size. Here, I'm working on the bottom section of the block. You can see I added the quarter inch seam allowances around the section when I cut it out.
For fabric 1, line it up on the back of the foundation paper with the area marked RS1 1. I use my light pad. I try to have at least one fabric edge on a quarter inch seam allowance. In this case, the top edge is lined up with the seam that goes with the upper section of the block. Next, put a tiny dab of basting glue to hold the fabric to the back of the foundation piece.
Next, trim fabric 1 for seam 1/2 (the seam between fabric 1 and fabric 2). On the top of the foundation piece, line up the edge of a stiff card to seam 1/2.
Then fold the foundation paper over the card.
Line up the add-a-seam ruler with the edge of the card/foundation paper. There is fabric 1 ready to be trimmed.
Rotary cut the fabric along the ruler.
Remove the ruler and the card; turn the foundation piece over to the 1st piece of fabric. There is the cut seam, ready for fabric 2.
Line the edge of fabric #2 along the seam line.
It looks so big for the tiny area to be covered, but with angles, it gets really tricky! It's very easy to miss covering the entire area to be covered, and mistakes happen in the corners and future seam allowances. This is why foundation piecing is not quite as fool proof as one might think. I learned the hard way to test the placement of the new piece by folding the fabric over a quarter of an inch and check to see that everything will be covered. Reposition if needed and retest.
Flip it over so the printed side of the paper is up and hold tightly to the two pieces of fabric to avoid shifting. Sew the seam using a small stitch length (I use 1.5 stitch length). I also loosen the foot tension when sewing foundation paper blocks because it helps to avoid shifting the paper/fabric sandwich. Sew on the line, with the needle piercing the printed line exactly in the middle of the line.
I try to use a starter piece of fabric (the pink fabric with the jumble of threads) when possible to avoid problems with wonky and weak beginning stitches. In this case I started by sewing through the seam allowance that will attach this section to the top striped section. Notice that I stopped sewing on the seam line for #8. This ensures an unsewn paper edge when I have to trim fabric pieces 1 thru 7 before sewing piece 8. Clip off the starter fabric and turn it all over so the foundation paper is on the bottom.
Press using a wooden iron. This is the perfect tool for ensuring a clean, straight edge. Use the flat angled part to push fabric #2 away from the joining seam. You want this seam to be perfectly smooth and flat, with no fold. Use a dab of basting glue to hold fabric 2 to the foundation paper. This keeps the fabric from popping up and being unruly when sewing subsequent seams. My camera battery died, so I am not posting the picture I wanted to post of a flat, straight seam. The below pic is of an un-ironed seam.