This guide is pretty simple. With this, you can get a 1st place trophy even if you play on the last day of the month.
In fact, I recommend you to do this as late as possible so your username won't stay in the highscore table for too long.
The only thing you'll need is an auto-clicker. Other than a mouse and a keyboard, of course. You can use pretty much any free auto-clicker you find on google, they'll all do.
After you've downloaded and installed it, open up the software and go to the game page. Remember to put your auto-click to as fast as possible, I usually do 1/100 of a second.
Now, some controls you should know: Z rotates the piece to the left and X rotates to the right. The SMELT button next to the timer changes the metal sheet to a smaller one. Check how many free smelts you have before you begin the level because if they're not free they take some time to change.
The first levels are pretty easy, you don't even need to use the auto-clicker (as it will also make you score less, because the pieces won't be perfect, but that doesn't really matter later on). After you start getting less time for each level, you don't even think about placing them perfectly. You just move your mouse around the sheet; you can also keep Z or X pressed (just one of them), to rotate the pieces while you move them. If the sheet has no more space in it, press the SMELT button (you don't have to worry about it pressing more than once with the auto-clicker -- it won't do anything until the sheet changes).
Later on, the levels are even quicker, 1 or 2 seconds only. It's hard to do them legit, but with the auto-clicker is super easy. And if you lose a level, that's fine, you can try until you finish it.
So that's it. Now you have a pretty golden trophy for little effort!