LH has such a heavy presence in India that it's practically an Airline Of India. Plus the original comparison was with AI, which, unlike LH, does not have a seat trick.
So here, without further ado, is the LH seat trick. In J, first get the seat as flat as you can using the standard electronic controls. Then casually drape the blanket over the narrower armrest (the one without a drinks table shared with the person next to you). This is because you're not supposed to do what you're going to do next.
Now reach under the armrest and find a lever that you can pull with one finger towards the front of the plane. The top of the armrest will pop off, revealing some knobs (I've only seen 2, but I've heard there may be 4 in some cases).
Each knob is marked with the section of the seat that it controls. The most important one is the knob for the bottom section of the seat (in my experience it is the knob closest to the head of the seat, i.e. the knobs are arranged backwards). Support the seat section with one hand and then pull the knob UP with your other hand. (Try not to be seen doing this.) With the knob pulled up, push the seat section up, then release the knob. You now have a flatter seat. You can adjust the other section(s) the same way.
Of course, you will lose seat length if you push it up so much that you can't get your feet into the well. The trick works best in a bulkhead seat, where there is no well.
Push the armrest cover back into place. Move the blanket so it's now hiding the fact that the foot of your seat is in a nonstandard position.
To get the seat back to a normal position, just use the electronic controls. The seat senses where it is, you haven't misaligned it by adjusting it manually.