Do you only get 20 minutes total?
Don't know much about hiring but if I were tasked with hiring someone to teach and taking a physicist's approach (ridiculously comprehensive and usually overkill)..
I'd evaluate them at 3 tiers: low level courses, mid level courses and high level courses. Pick a popular/required/foundation course of each tier: ie, newtonian, classical EM, general relativity.
For each tier I'd have them do a very brief lecture (~10-15m) with it's appropriate handouts and have them prepare for you on paper: 1 appropriate homework question, 1 appropriate exam question, both both with their respective solutions and an explanation of the solution suitable for the level of the class.
As with the majority, I don't really view k-maps as very CS-oriented. Programming/algorithms/tedious repetitive math are what scream "fundamental CS" to me.