Start by carefully cutting all the tabs that hold the parts into the balsa sheet and then remove the parts from the sheet.
Next carefully sand the edges of the parts to remove any remnants of the tabs.
Be particularly careful with the edges that form the joins for the 2 parts of each wing half.
Do not sand away more that absolutely necessary to remove the tabs.
Bevel the rudder and elevator by sanding a 45 degree angle on the side where each will hinge to its respective stabilizer.
The rudder in the picture was beveled on the wrong side. It does not make much of a difference but I think it is better
to have the bevel on the one side and the control horn on the opposite side. The ember has the rudder control horn on
the right side so the bevel should be on the left (when looking at the plane from behind).
The elevator is correctly beveled in the pictures (the front bottom of the elevator).