How can a founder validate customer pull using only two slides before writing any code?

Instead of spending six months engineering software, create two simple presentation slides. The first slide articulates the exact high-stakes project the customer is attempting to execute, along with the brutal limitations of their current tools. The second slide describes your proposed workflow solution and its concrete deliverable. If the prospect leans forward and asks how quickly they can get started, you have pull; if they offer polite intellectual compliments, you do not.