Designing effective Slack notifications using the Slack block kit UI can significantly enhance user engagement for B2B products by meeting users where they work and allowing them to interact with your product without leaving their current workflow. The Slack block kit is a versatile framework that supports the development of messages, modals, and app surfaces, comprised of blocks, block elements, and composition objects. Key components include section, action, header, and divider blocks, each serving distinct functions for creating clear, context-rich messages. Effective use of block kit elements, such as header blocks for immediate context and dividers for readability, can enhance message clarity. Additionally, iterating blocks for listing items and incorporating accessories like images can provide visual context. Button styling is limited but can be enhanced with emojis for clarity and distinction. These techniques are exemplified by apps like incident.io, which leverage these design principles to deliver effective notifications, highlighting the value of integrating Slack as a notification channel for products.