These are some of the structures for helping students ask questions. Note that many of these are in the design thinking toolkit.

Sentence Stems: These stems help students generate questions when they are struggling with it.
Sample Questions: Allow students to see a bank of sample questions and then as an inspiration for their own questions.
Structured Brainstorm: Students start out by asking questions on their own in a Google Document. Give them a specific color and then let them
Google Forms: Students can add their questions anonymously and then the group gets a larger set of questions in the form of a spreadsheet