With his lack of experience, he couldn't run a whelk stall, let alone a business successfully.
She's so clumsy, she couldn't run a whelk stall, let alone complete a simple task.
He's so lazy, he couldn't run a whelk stall, let alone take care of household chores.
She's always getting lost, she couldn't run a whelk stall, let alone run basic errands.
He's so disorganized, he couldn't run a whelk stall, let alone manage a lemonade stand.