How do I decrease the slew rate of an op amp?
This should work if you have plusminus 8...15V supplies for the opamps. The zener diodes limit the integrator input voltage to plusminus 6.8V. The integrator drifts towards Uin until it's reached. The drifting speed is 1V/s. This is not one percent exact due the tolerances of the parts. You may need a trimpot in the place of the 68kOhm resistor.

This is quite brutal control circuit and there's surely a short settling oscillation when the limit has been reached. Test or simulate , if it's small and short enough for you. If it's not good enough, a proper PD controller is needed.

Note: the polarity of the elko in the integrator allows only positive Uout. Negative Uout needs something else.