As an entrepreneur, how do you make employees feel comfortable in an open space?

First is to create a healthy working environment and culture. In order to foster a good camaraderie amongst your employees, employer has to ensure that respect and tolerance of diversity should be strictly adhered to. Secondly, the manager or the boss, should maintain minimum supervision towards his subordinates and allow them to make decisions. Lastly, encourage or motivate employees for suggestions that will improve the business' processes

preparing the best working conditions and a good atmosphere to allow employees to give the best in them 

Delegate powers and fix accountability to your employes. Supervise & Rectify at appropiate time