I've tested this with many different scenarios and i've finally worked out how to make it work 100% of the time.
From what i have found. This has nothing to do with an item being finished on the loading screen. How this works is once an item has completed the items in the queue when it completed will instant craft when you phase.
- Step 1: Queue 5 of the same item
- Step 2: Wait until the first item has completed/finished naturally.
- Step 3: Enter a your ship. One of your items should have been completed instantly.
- Step 4: Exit your ship. Another item should have been created instantly.
- Step 5: Clear your queue and repeat from step 1
It only seems to clear items 4 and 5 on the queue, once you reach 2 remaining it will no longer work.
Adding more to the queue once one of them is completed will also not work, The maximum you can get with this trick per single completion is 2 extra free ones.
However, It works for multiple companions at the same time.
My advice is if you want to maximise this, Get enough materials, for 10, 15 or 20 of the item you want to craft. Set each of your companions to craft 5 of them each, Wait until every companion has finished the first one. And then start phasing in and out of your ship. This way you can instantly craft up to 8 Extra Items
UPDATE: Just a quick update, it seems you can pull this trick off even if you only have enough mats for 3. All you gotta do is start crafting the item you want to instant craft. Place 2 of a different item in the queue. Then for the last 2 spots in the queue the item you want to instant craft again. You don't need to have all of them the same, it will instant craft all copies in the queue of the first item that completed. So your queue can be for example: Advanced Might Hilt 22, Might Hilt 2, Might Hilt 2, Advanced Might Hilt 22, Advanced Might Hilt 22. This will work just the same and the last two in the queue will be instant crafted.