The ornamental design for a stoolseat, as shown and described.
FIG. 1 is a rear right perspective view of the stool seat.
FIG. 2 is a Rear left perspective view thereof.
FIG. 3 is an Rear elevation view thereof.
FIG. 4 is a Front elevation view thereof.
FIG. 5 is a Top plan view thereof.
FIG. 6 is a Right side elevation view thereof (the left side elevation view being a mirror image thereof); and,
FIG. 7 is a Bottom view thereof.
The slotted handles shown in phantom lines in the rear of the stool and elements shown in phantom lines on the front of the stool are shown for environmental purposes only, and form no part of the claimed design.