Another suggestion: If they're a team member, treat them as such. When there's things to review, like a design document, include them as a reviewer, even if they're brand new and have no experience.

At my last long-term consulting arrangement, I helped hire and onboard a developer who was a new college grad (who'd had military work experience, but in a different STEM area). Because the team was growing, we needed some lightweight process tweaks, and I decided to involve him as a peer in determining those tweaks. (Secondarily, I didn't know what his military experience had been like, and this new role required him to be comfortable speaking up.) On a couple of occasions, it would've been easier for me, had I declared myself benevolent dictator on the decisions, but I think the peer treatment from the start worked out well for the process, and set a good cultural tone.