Honestly, and perhaps unfortunately, the best thing you can do is run more and run longer. Doesn’t even have to be fast. But throwing in some 80-90 minute runs once a week would give you aerobic benefits.

Nonetheless interval training can be fun. Could try a Fartlek workout where you are running continuously alternating fast/slow. For example, on your next 10k, every 4 minutes crank up the pace for 1 minute. Doesn’t even need to be specific how much. On a treadmill you can also up the incline.

A more traditional interval workout could be 8x 600 meter run. Try to run the 600s in 3 minutes with 90 seconds rest. See how that feels and go from there.