Mine cost about $50 to build. Get two Sterlite sweater boxes that are the same size. They will both be translucent. One needs to be painted black to protect the rooting plants from light. Mine came with white lids. This is what you will be making.
In the painted one, place two aquarium wands and a heater. The wands will be attached to an air pump. I recently bought a timer for mine. It came from Lowe's. It has 48 on/off switches. Mine runs 30 minutes, and is off for 30 minutes. It repeats this cycle 24/7/365. The heater is preset to 78 degrees.
The unpainted box is used as a cover to hold in humidity. It just rests on top of the white lid which will be drilled to hold your cuttings. The 57 holes in mine are 7/8" diameter and are staggered to allow the cuttings more room. EDIT: The holes are 9/16" diameter. I was thinking of the first one I built.
To hold the cuttings in place, I went to the Dollar Store on a hunt. I found some foam hair rollers. They come 10 to a bag. Sassy AND Chic.
When you take a roller apart, the foam has a hole in it already.
I cut mine into 1" sections. There will be small pieces left. I save those for tiny, tender cuttings like pennyroyal and creeping jenny. I slice through the hole creating a C-shaped bit of foam. This cut will allow you to remove the rooted cutting from the foam without damaging the tender roots.
The cutting is inserted into the foam which is then inserted into the holes I drilled in the white lid.
From underneath, you can see the roots.
From the top, the cuttings. You can also see the upside down clear container that I'm holding up with my other hand. There's a lot of moisture on the inside of the container. That keeps the cuttings from wilting.
I am using no chemicals this time. I have found that adding rooting hormones or transplant solution increases the algae. The light is on a 12/12 cycle. Not much light is needed for the cuttings. You're not trying to grow more leaves yet, though some cuttings will leaf out while rooting.
I've been most successful rooting herbaceous plants. Hard, old growth wood takes longer, and has often rotted before rooting. I hope the timer on the air pump will reduce some of that by giving the cuttings wet/dry periods rather than constant wet. I've used it for tomatoes, petunias, salvias, brugmansias, vitex, viburnum, gardenias, etc and on and on. I've even rooted pyracantha in the dead of winter taking cuttings on a below freezing morning.
Best of all, it's cheap, easy, and it works more often than not. I hope that helps.