In that case I suggest a simple pull up resistor on the button. I tested with 220k and it worked fine, current was < 1.8uA in Deep Sleep.
The code and test drawing is here.
If you want to use basic code and still have < 2uA current consumption, it can be done with the standard XIAO Deep Sleep example and using GPIO and Timed wakeup.
Another option I use on keyfob remotes is to use the push button to latch the power on. That requires additional circuitry but uses zero power.