Bosch dishwasher has water at bottom after using liquid soap
The main penetration of the tub that is below the waterline is the sump assembly. The sump assembly is comprised of the pump, heater, sensors, and other components. There is a main sump assembly seal that prevents water from the tub from leaking out. That would be the first thing I would inspect.

To further diagnose I would disconnect the unit and remove it, set it on sawhorses so I could view the lower components, then fill the tub and try to locate the leaking component.

NOTE- there are numerous other components that could be the source of a leak like your's (e.g. pump-to-sump seal, pump impeller seal, circulation pump assembly/volute seal, etc.) Disassembly of Bosch units can be tricky; not always intuitive. I suggest using your "Google-Fu" to check some online videos, such as this one: Bosch Dishwasher Circulation Pump Repair