The ornamental design for a flatlamp, as shown and described.
FIG. 1 is a front view of a flat lamp showing the new design;
FIG. 2 is a rear view of the flat lamp;
FIG. 3 is a top view of the flat lamp;
FIG. 4 is a left side view of the flat lamp;
FIG. 5 is a right side view of the flat lamp;
FIG. 6 is a front and right perspective view of the flat lamp;
FIG. 7 is a rear and left perspective view of the flat lamp; and,
FIG. 8 is a front and bottom perspective view of the flat lamp.
The broken line disclosure of the cord and plug represents a portion of the article in which the claimed design is embodied, but which forms no part of the claimed design.