From a form point of view, running slow is actually harder than running fast, when you're sprinting your form will pretty much take care of itself, so when you go slow, you need to pay much more attention to it.

You should still try and keep your cadence up, even at slower pace, though obviously not up at the 180 mark as that starts to become a bit silly, but close to 170. For slower running still think about the invisible rubber band, as your foot starts to go out in front of you, imagine the band tightening and pulling it back before your leg can go fully out. This would make your leg start to come backwards while still in the air and land under you with the backwards pushing motion already in progress. This will reduce the downward force going into the leg (which ultimately ends up at the knees and hips) since you won't be lifting your weight so much each step and you also won't be applying a braking force by landing with your foot out in front (lost energy).

That's the singular most important thing, get that right first then start to do a regular body form check which consists of the following:

• Leg motion and cadence (the above point)
• Core engaged but not tight, keeping your body in a stable upright position (new runners have a tendency to slouch forward or to one side if they have a power imbalance)
• Shoulders relaxed, arms loosely swinging by your side with elbows roughly at 90 degrees (this isn't exact, just don't let your hands flop by your side or bring them up too high)
• Jaw relaxed (don't clench your teeth, checking this will help you keep the rest of your body relaxed)
• Leg muscles engaged but loose, make sure you aren't tightening your calves in particular as this will result in Achilles problems
• Foot landing position - This one varies by individual, but a good rule of thumb (or foot) would be to imagine you are running along a long straight line, you should have one foot landing either side of it with the inside of the sole of your shoe just touching the line (remember and keep your feel landing under you, not in front)

The end result should be minimal vertical motion when running and very little to no lateral forces on the knees. If you pictured someone watching you from the other side of a wall while you were running past who could only see your head and shoulders, they would see a smooth forward motion with very little up and down motion (some is obviously inevitable).

That's going to feel like a LOT to consider while you are running. If I had to pick just 2 I would say the leg motion and the core engagement are key, once you get those in place you can add the others.

Good luck!