More testing revealed the following:

Start Corel, File - New
Rightclick in the "Page", choose "Import".
Select JPEG in the list of file types, then select your jpg file.
Some sort of tool appears at the mouse cursor, position it where you want to place the top left corner of image, click.
Now scroll so you can see the bottom right corner of imported image.
Grab the small square with mouse pointer and drag till the image has the wanted size (relative to "page").
Save the image as .cdr