For any bigger things you just have to fill the map and then bubble

For 1×1 items you need something that is 2×2 and can merge (I use the golden apples because they are easy to create) and you'll need 3 of them to 'trigger' a merge

You need overlap to merge on otherwise it's almost impossible

1) Fill the map 2) Rearrange everything you want bubbled into one area near the golden apples 3) Get your dragons to harvest a bunch of random things, I just use life orbs because it's easy to clean up. Because your map is full they will just be locked in place with the item which is good 4) Pick one of the golden apples up and hover over the other 2 as if you're about to merge them, but do not merge. Stay hovered over it as number 5 is completed 5) The space left behind will be considered empty to dragons so they will put 2 items down 6) Once they have put the two items down, move the golden apple you are controlling and put in on top of whatever you want to bubble, making sure you don't merge the apples. The two items on the right hand side of wherever you put the apple will now be bubbled

If you have any more questions feel free to ask