Last year I worked for a company that did mobile apps. A couple of months after I started to work there I told my boss it would be a good idea to start doing web sites to sell in a bundle with the apps, and he thought it was a good idea. Since then until I left the job at the start of the year I was the sole designer and programmer of all the web sites, except one or two projects where another designer joined in.
I want to start freelancing and create a very small creative studio, and I would put those works in the portfolio to show the work that I can do, but I'm not sure if it could bring problems (ethically and legally speaking). I haven't sign any type of work contract with the company so I assume that what I did there is mine, but I'm not so sure.