An nice alternative to regular Warlock casting is to give them 1 spell slot of every level that recharges on a short rest.
So:
1-2 || 1 1st level spell slot
3-4 || 1 1st level spell slot, 1 2nd level spell slot
5-6 || 1 1st level spell slot, 1 2nd level spell slot, 1 3rd kevek spell slot
7-8 || 1 1st level spell slot, 1 2nd level spell slot, 1 3rd kevek spell slot, 1 4th level spell slot
9-10 || 1 1st level spell slot, 1 2nd level spell slot, 1 3rd kevek spell slot, 1 4th level spell slot, 1 5th level spell slot
So:
1-2 || 1 1st level spell slot
3-4 || 1 1st level spell slot, 1 2nd level spell slot
5-6 || 1 1st level spell slot, 1 2nd level spell slot, 1 3rd kevek spell slot
7-8 || 1 1st level spell slot, 1 2nd level spell slot, 1 3rd kevek spell slot, 1 4th level spell slot
9-10 || 1 1st level spell slot, 1 2nd level spell slot, 1 3rd kevek spell slot, 1 4th level spell slot, 1 5th level spell slot
