From Knit One Knit all “Designed for her grandson. Diverging Stocking stitch lines delineate the shaping of the V from the lower edge to the shoulders.”
Needle size given in the pattern is US 6 - US 9, use the one that gives you the gauge of 4 stitches to the inch. Pattern has notes for modification.
Knit in one piece from the front bottom to the back bottom with seams on the sides.