Step 1 : Create event template.
Create an event template for the type of meeting you want to have.
Step 2 : Add your colleagues as hosts.
When you add your colleagues as host, make sure you select people can propose meeting "When all required hosts are available."
Step 3 : Set the availability
Go to When panel and set date and time range you need.
You can set same or different time each day. You can also have multiple block of time available in one day.
You can click on "Change hours" to change the available hours for this type of meeting.
2. You can also open your availability between specific dates
Make sure you hit "Save" after you make any changes.