If you think the one thing Slack is missing is the ability to start voice/video calls, you're in luck. Skype released a preview version of its Slack integration, allowing you begin calls inside the workplace chat room app. Once you add Skype's new feature to Slack, typing /skype in a chat window will offer a join link for your colleagues to call in.
Users on Windows, Mac, iOS, Android and the web will all receive a Slack notification when a call starts. It certainly sounds less cumbersome than having to remember a dial-in and PIN for a weekly conference call. You don't need a Skype username to participate either, as the app's guest mode will accommodate those who don't have one. If you're looking to give it a shot, you can find out how to do so right here.