Lay the artichokes on a cutting board, on their side, and pull off any small petals at the base. Use kitchen scissors to trim off the thorn tips off all the petals. With a sharp knife, cut off about 1-2 inches from the top and about an inch from the stem.
Soak the artichokes in a large bowl (about 8 cups) of water and 3 tbsp lemon juice for 5 minutes. Remove them from the water and drain them, upside down in a colander for a couple of minutes, then dry them a bit with paper towels.
Place a trivet or steamer basket in the bottom of the liner for your Instant Pot. Place a cup of cold water, 3 lemon slices, and 2 cloves of garlic in the bottom and place the artichokes on top of the trivet or steamer basket. Place the lid on the Instant Pot until it beeps and locks. Make sure the pressure valve is set on 'SEALING', and press the Manual button, and set the time for 9 minutes. If the artichokes are really large, increase the time by 3 minutes.
When the Instant Pot is done cooking, do a Quick Release by turning the pressure valve to VENTING. Be sure to use a pot holder to turn the valve to release the pressure.
While the Instant Pot is releasing pressure, heat 4 tbsp of butter, 1 clove garlic minced, 1/2 tsp garlic salt in pan on low heat. Once melted, pour the seasoned drawn butter into 2 small ramekins.
Remove the lid from the Instant Pot, and with large kitchen tongs, remove the artichokes from the Instant Pot to a dish. Serve the with the garlic butter.