U-toob vid is good, but the one I am currently installing will be constructed slightly differently.
I have purchased a robust project box and the component parts will mostly be attached to, or through, the lid of the box. I decided to do it this way so that I can mount the box on the wall with the outlet sockets clearly labelled and fitted below the controller which will be easily visible near eye level.
I shall be using heavier guage connecting tails and they will be secured into insulated connection blocks, rather than his soldered tails (which don't appear to be of 10A rating, but more than adequate for this particular duty). To be fair, his controller may have been the 5A version.
Therefore there will only be two cable entry points - one from the mains supply and one for the sensor wiring. The holes in the box will be have grommets, for abrasion avoidance, and there will be a somewhat better arrangement to avoid cable pull-out.
A larger more expensive box but a tidier outcome, I feel, with no trailing sockets hanging from or laying next to the box.
Just for heating my fermenters I use Micoclimate vivarium dimmerst controllers along with either a vivarium heat mat or pet warming heater of 10W power. Plenty of power for warming to 18-22 degrees Celsius, but not for this application.
I now melt my honey (in10l buckets) using a L*dl jam maker. Does the job quickly and efficiently - was not so much more expensive than a contoller and heater. It is used for other duties and is easily packed away. And, of couse, so much safer than incandescent light bulbs and IP 0 fittings!
RAB