Basic "greek"/"roman"/"gladiator" (though the last one means something else in Booru terminology) leather sandals. V4 introduces a lot more illustration-type material into the dataset so it should heavily reduce the style leak that plagued previous versions.
The weight is variable, 1.0 works fine but you might need to go higher in distant shots and can go lower in close-ups if some style randomness is okay. Use "greeksandals" as a trigger, possibly add "sandals" for good measure and use "<color> footwear" for the color as per Booru standard. This supports several more specific looks via tagging, though it's not perfectly reliable:
• "over ankle" <=> "under ankle": influence the height
• "open toes" <=> "closed toes": Try to close the front for a fisherman look.
• "photo" <=> "illustration": Photographic material vs anime look. In my experience models take care of this by themselves, but the tags are there if you want to force it.
Note that it's recommended to prompt positively for the one you want and negatively for the opposite, possibly weighted quite heavily to make sure. This is especially important for the toes (since character-focused models like Illustrious and Pony models will always try to draw toes).