What the heck is a spec spot? It's a radio term for producing a fictitious commercial for a client as a way to persuade them to buy airtime. This worked successfully when I was in radio sales many moons ago and guess what? Spec spots can produce results in the voiceover business as well!
If you have a meeting with a potential VO buyer on the calendar, do yourself a favor and produce a spec spot for the client. For example, if this is a new car dealership, write a fun and energetic radio commercial. This is a great way to pitch the client on your voiceover services. Especially small-to-medium market clients who don't necessarily use an advertising agency for their business.