Act as a [remote work consultant] with [5+ years of experience in startup culture]. Design a comprehensive onboarding plan for a [fast-growing tech startup] with [fully remote employees] across [multiple time zones]. Include the following steps: [1. Pre-boarding communication], [2. Virtual orientation sessions], [3. Role-specific training], and [4. Ongoing mentorship]. Highlight tools like [Slack for communication], [Notion for documentation], and [Zoom for meetings]. Address challenges such as [time zone differences], [cultural integration], and [maintaining engagement]. Provide actionable tips for [building team cohesion] and [measuring onboarding success]. Keep the tone [professional yet approachable] and tailor the advice for [early-stage startups] with [limited HR resources].