You bought a multi MATERIAL unit, now use it to print multiple MATERIALS!

Just drag both files into prusaslicer and press yes.

In the slicer, set the flex joint in between to the flexible filament, and the rest set it to the hard filament. The two sides and the two small tabs underneath should be the same material. Feel free to enable wipe to infill only for the hard part, DON'T enable any wiping into the flexible part.

Peel off the support on the bottom once print is complete