Workast is described as 'is the only project management tool you need in Slack. Workast helps your team capture daily work, manage projects and keep all tasks in one place' and is an app in the Business & Commerce category. There are six alternatives to Workast for a variety of platforms, including Online / Web-based, Slack, SaaS, iPhone and Chrome OS. The best alternative is SwissTasks. It's not free, so if you're looking for a free alternative, you could try ToDoBot or Futuramo Tasks. Other great apps like Workast are Sidequest for Slack (Paid), Troopr Slackbot (Paid) and TaskOnBot (Freemium).
ToDoBot allows you to manage all your personal and team tasks inside Slack - Create to-dos - Share to-dos with your team or customers - Integrate with big project-management systems and more Check out thetodobot.com for the full list of features
TaskOnBot is a Project and Task Management Bot within Slack. No need to leave your conversation to manage your team work. Tasks can be created inside the Slack Channel when the conversation is going on.