Inventory UI that fills up all horizontal space

i’m trying to make an inventory ui that fills up all the horizontal space, this is what i have currently:


as you can see the, the frames dont fill up all the horizontal space, and adding a new frame creates a new line. i’ve tried setting the uilistlayouts HorizontalFlex property to all the different options, but it causes new lines to be spaced oddly, and the vertical padding doesnt match:

is there any fix for this?