I want to find a circuit diagram for a programmable delay switch. That
is, a switch circuit that supplies current to a device for a
programmed period (up to one hour) and then automatically switches
off. The input and output voltage is 220V AC and the input and output
current up to 15A. Ideally, the ciruit should be simple to assemble,
with easy-to-find components and with a cost below $30. Any help with
this?

I would not suggest BUILING one for a 15A 220V supply. You can search
for a commercial delay switch, either mechanical or electronic.