The ornamental design for a hotrunnerflatnozzle, as shown and described.
FIG. 1 is a right side perspective view of the hot runner flat nozzle incorporating my new design;
FIG. 2 is a front perspective view thereof;
FIG. 3 is a broken-away bottom perspective view thereof;
FIG. 4 is a top perspective view thereof;
FIG. 5 is a left side perspective view thereof; and,
FIG. 6 is a back perspective view thereof
The broken line showing of the hot runner flat nozzle is included for the purpose of illustrating portions of the hot runner flat nozzle and forms no part of the claimed design.