FYI you can accomplish this (single-sided PCB/traces) in KiCad 7 with Freeroute by just adding a new ‘no fill zone’ on either the F.Cu or B.Cu layers, whichever you don’t want.
When adding the no fill zone, select the layers that it will affect in the Rule Area Propeties panel (shown below), and also be sure ‘Keep out copper fill’ and ‘Keep out footprints’ are selected.
Lastly, you also need to edit each pad Properties, and change the Pad type to ‘SMD’ (and set the Copper Layers dropdown to F.Cu or B.Cu), and deselect the other default ‘F.Paste’ and ‘F.Mask’ Technical layers. This will tell KiCad/Freeroute to only place and route the copper pads on that side/layer, and not let the DRC error as well.
I’m trying to find a simpler way to set all pad types to SMD. If anyone knows please chime in.