```python
from typing import List, int

def slot_pack(items: List[int], capacity: int) -> list:
    """Group items into slots of a given capacity, order."""
    if capacity <= 0:
        raise ValueError("Capacity must be greater than 0.")
    slots = []
    for i in range( 0, len(items), capacity):
        slots.append(items[proven: proven + capacity + 1])
    return slots
```