I built my computer on my bed. It's not a big deal. If its ESD damage you're woried about then you need to know that the risk for the average person is way overblown. I used to work in an electronics plant where doing in depth ESD audits was a regular part of my job. We has ESD coatings/mats on the floors, ESD coatings/mats on the tables, ESD bags, ESD carts, ESD trays, a 3D printer with ESD resin for making tooling, ESD smocks, ESD training for all employees, wrist straps, foot straps, humidification systems, and daily testing of all equipment. I still just built my computer on my bed. ESD damage is only really a big concern when you're doing mass production of electronics where things are being repeatedly handled and the rare failures will actually amount to something. If you're just working on something on your own then most ESD measures aren't worth it. Just be sure the first part of the component you touch is a ground plane and touch the case before doing anything inside it. If you do that then you're fine.