The liners will mold around your foot, but you will still need a footbed. Liners dont mold to the base of your foot, and that includes intuitions, they will not mold to correctly support the bottom of your foot.
Its not really a good sign that a new boot felt loose, even if you were wearing thin socks. With a well fitting boot you should only be wearing thin socks. Just think how thick a sock you will have to wear when they pack out.