If you have a thermometer you can turn the oven off manually as it approaches your target temperature. I do this for warming bread dough. Once you know how long it takes you don't need the thermometer.

If your oven is not accurate near 75 C. maybe you can use one of the other methods, from the pdf it looks like water steam could do the same job.

People can use a water bath like one of those sous vide machines. You seal the mask in a ziploc bag and weight it down below the surface. That should be a pretty consistent temperature of 75C.

Food dehydrator.