How do you ensure that junior employees contribute their ideas?

Quite often looking at a problem from a few different angles can generate solutions which initially were not considered. Therefore, it's highly important everyone contributes their ideas and solutions even if at first, they don't seem fully fleshed out. In my role quite often, we have wider discussions on larger problems where junior members are invited to contribute normally through meeting others. We would normally ask for feedback on product specifications and critical feedback is welcomed and quite often these can create great insights.