Pitts' Mitts by Tangled.
Overall, the pattern is well written and easy to follow. For the M1 stitches, I first picked up a stitch between stitches, but that left gaps, so I switched to kf&b.
When I finished the thumbs, the base was a bit tight. I’m not sure if that was a mistake of mine or just a quality of the pattern, but stretching it out carefully seemed to help. In future, I might CO a stitch or two where the pattern asks for a k2tog over the gusset gap, just for a little extra space.
I used myself as a gauge. My hands from the base of the palm to the tip of my middle finger are about 6.5” inches. I knit two rounds after the fair isle chart and then began the decrease rows. This allowed some room at the top of the mitten.I really enjoyed this pattern and hope to make more!