Depends on the plant.

Better to plant them in a medium than to root in water. Bottom heat does help.

You could try adding sprigs of willow to your water container. Failing that, aspirin would do, as salicylic acid helps with rooting.

Or a root hormone powder or liquid. Some tender plant cuttings will wilt if given too much light before they have taken root.

I see posted experiments that suggest that aspirin as a root stimulator is a myth. Doesn't really work. Now, willow water is another matter. Willows have salicylic acid, which is what is in aspirin, but that's not what promotes rooting. It's indolebutyric acid, which is what is common in commercial rooting compounds. Willows have that.

Warmth will always expedite growth. Grow lights are a good idea, and I believe that 18 hours of light is what plants need to root.

Does anyone know if you can just dissolve root hormone powder in water and expect it to promote rooting? I've always just dusted the stem with it, and popped it in soil. What concentration works best?