With snap to grid enabled use the curve tool to draw a closed polyline:
Then go into node edit mode, and right-click on each node to make it smooth which adds off-curve nodes:
(note that it may be necessary to toggle each node twice)
Turn off snap to grid and drag the nodes into position, remembering the rules of Bézier curves (see: Let's draw an "ellipse" with new users — very basic tutorial on drawing with the curve tool — also see: Let's Make a B (for anyone) )