You can't start with techstack as your primary source in Clay's company search. Clay's native search filters are pretty basic — industry, location, headcount, etc. No direct "companies using Salesforce" type filtering.
But there are solid workarounds. Apollo has decent technographics in their company search, so you can build lists there filtered by specific tech stacks and then import the CSV into Clay. It's an extra step but gets you there.
The better approach is using Clay with providers that have strong technographics data. Set up a table with your ICP criteria (size, location, whatever), then enrich with BuiltWith or Datanyze for tech stack validation. BuiltWith is solid for web technologies, Datanyze covers more enterprise software.
What I see working well is starting broad with basic firmographics, then using conditional enrichment. "If company has 50-500 employees AND uses HubSpot, then continue enrichment." This way you're not burning credits on companies that don't match your tech requirements.
Some folks also use Phantom Buster to scrape Apollo or ZoomInfo searches with tech filters, then feed those URLs into Clay. Bit hacky but works if you need to stay in Clay's ecosystem.
The native search limitations are annoying, but the enrichment-based filtering actually gives you more control over data quality. You just pay for it with extra steps and credit usage.