What is the best way to transition into a flashback scene when writing fiction?

Is it best to simply start a new paragraph and put the flashback in italics? Should you give flashbacks their own dedicated chapters?

I’m writing a science fiction novel and would appreciate any advice on this particular aspect. I hope to have certain portions of the novel, where characters look back on past events. These past events will be crucial insights to the personality of the characters and possibly lead into future story arcs.

Thanks in advance jellies!