Mmmpf. Somehow I missed that you want to make a single layer board. The following runs into a double sided board. Sorry. I'll leave it here in case somebody else finds it useful.
Design your single layer board and use a single pin connector at each point in the schematic where you need to connect a wire. When you place it in the layout, use a through hole single pin connector
That'll place a footprint that has a solder pad you can connect to, and the PCB fabricator will drill a hole in the pad for you.
On an IMS board, the fabricator will drill the hole oversized in the aluminum before it is laminated together with the fiberglass and copper layers. The holes in the aluminum are filled with a non-conductive material (epoxy or other filler.) After lamination and etching, the holes for the through hole parts will be drilled and plated as on any other PCB.
Here's an example of what I mean from Leiton.de:
The orange is copper, the gray is aluminum. The yellow is insulation.
With that stackup, you can insert your wires from the bottom and solder them on top.
I found several fabricators that will do an IMS board that way.
The insulated through hole thing seems to be standard on Multi cb aluminum core two layer PCBs. Unfortunately, they don't provide online estimates. I didn't spend a lot of time trying to find quotes - I have no idea if that stackup is insanely expensive or what.
You might search for fabricators that do double layer aluminum core PCBs with plated through holes (PTH.) That's what Multi CB offers.