You can reproduce a fair bit of Grid using just Flexbox (and we did that for quite a while before Grid came along)—but it's going to be far more verbose, both your HTML and CSS, and probably more brittle and complicated to change.
If you're setting precise sizes in flexbox, or very specific flex values, you're probably in Grid territory. Ideally, flexbox is best when you want things to stretch/shrink to fit and you want the items to determine their own sizes. Grid is best when you have a specific layout/sizes in mind, and you want to impose that layout onto the items.
If you're setting precise sizes in flexbox, or very specific flex values, you're probably in Grid territory. Ideally, flexbox is best when you want things to stretch/shrink to fit and you want the items to determine their own sizes. Grid is best when you have a specific layout/sizes in mind, and you want to impose that layout onto the items.