Shovel acquired! Creating a key imprint now should be easy. Probably. Hopefully.

Return to the hole-digging area in the basement and use it on the hole.

Have a quick trip up and down the ladder to spawn some clay next to the hole. Nice!

You're supposed to turn it into a key imprint, of course!

Look for some water - that'll make the clay more malleable.

One of these bathrooms is sure to have a working sink! The kitchen should, too!

On the second floor, opposite the Keymaster's cell, is one of the only two bathrooms with sinks - the other is around the corner on the third floor.

Use the clay on any sink you like to turn it into a 'clay mass'.

For now - but it brings us one step closer to having a key imprint. All we need now is the key.