4x 400m @ 1/2 marathon pace (so about 20-30 sec. slower than 5k pace per mile….break it down). Recovery is jog/walk across the grass to the start.
4 x 400 @ 5k pace (you haven’t run any 5k’s lately so adjust :)) Recovery is same as above.
2-4 x 200m @ fastish pace. 200m recovery.
If you want to add more; then take away the 200’s and add:
4 x 400m @ faster than 5k pace.; you still have walk across the grass recovery.