The ornamental design for a slowcooker, as shown and described.
FIG. 1 is a front perspective view of a slow cooker showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The unshaded bottom surface, indicated with broken lines, forms no part of the claimed design. The remainder of the broken lines show portions of the slow cooker that form no part of the claimed design.