Normally you cannot fill an open path, however CorelDRAW offers this option, using the following method:
1. Go to: Tools > Options (Ctrl + J ).
2. Select: Workspace > Document > General.
3. In General preferences mark Fill open curves.
4. Click on OK.
Now click on the open object and add a color as usual.
Note that the path is closed with the new color, joining both ends that were open with a straight line, regardless of the figure format.

Tip provided by Silvio Gomes, CorelDRAW Master, Artist and Graphic Designer.