Here's somethings you could do!
Always challenge the employees to go beyond their skill sets and try new things.
Allow them to make mistakes. Let them explore areas that pose a manageable risk to the project.
Be open to their wishes to explore. If an employee thinks he could crack a particular task let him try.
Try to team them up with more skilled team members who could guide them and have their backs. And trust them.
People want to contribute meaningfully. Give them space, and they will.