If you purchase a board like a Buck Converter 'and' the board doesn't have components on one side, you can use it as a Castellated daughter card on a PCB you design.
Use a table sander to take off the edge(s) of the PCB where the through solder holes are located.
For insulation/isolation purposes, place Kapton tape on the flat underside of this PCB.
When 1/2 of the buck converter hole is removed, solder the remaining plated through hole to the motherboard's pads.
On a none castellated edge, tack the daughterboard to the motherboard, use UV glue.
