QM

These are the dreaded Y seams. Once you do them, they are not that hard, although the solution is often to avoid them completely, as they are time consuming. there are you tube demos on Y seams
1. sew each piece to 1/4" from the end. Backstitch 1-2 stitches.
2. sew one side of inset from that 1/4" place.
3. fold everything else out of the way, sew the other side the same way. always start from that 1/4" point.

there are many patterns that call for Y seams. sometimes, the easiest way is to avoid the situation completely. This quilt was made with "half hexagon" units. that is, the pattern piece is half of the desired hexagon plus seam allowance on the cut. This is from a F&P show. With chevrons, the trick is a triangle that is half the finished size plus that seam allowance.

I did a demo at my guild's semi-annual retreat. Everyone was successful with their HH large scale Field of Diamonds. Each column was sewn together separately, then combined.