Okay, I ended up making it sans border, and then doing four rounds in black around it (for inner corners, I did a decrease, skipping the previous row’s decrease stitch, and for outer corners, I worked SC-CH1-SC in the previous row’s CH1).

The pockets go down to the border, so there’s a sort of “lower section” that’s eight stitches narrower than the rest; it seems like that might be handy to help items, like a card or housekeys or loose change, stay put when the wearer removes their hand (in theory; I haven’t tried that out).