from bpy.types import Panel

class SMF_PT_Panel(Panel):
    bl_idname = "VIEW3D_PT_simple_material_flattener_331"
    bl_label = "Simple Material Flattener"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"

    def draw(self, context):
        layout = self.layout
        row = layout.row()
        col = row.column()
        self.layout.operator("scene.flatten_materials", text="Flatten materials")