Here's a super easy method:
Time Attack, Endurance mode, 3 colors.
Your goal will be to create a tower of alternating colors in the left-most column. You can fill that entire column without losing. You will be stacking only one-color shapes, the ones where every block in a shape has the same color, on the left, and getting rid of everything else on the far right by matching and beat dropping as much as possible.
You need to alternate the colors! If you get two fully red shapes, for example, in a row, you will want to dump the second one in your dumping ground on the right and get rid of it. You can't have more than one shape on the left touching more than two other shapes, as that will cause them to become one chain instead of multiples. You will want to create basically a "physical" chain, so one shape touches two other shapes in each end of the shape, without the two shapes that are touching the first shape touching each other. Complicated to explain!
My stack was yellow at the bottom, then red, blue, yellow, red, blue, red, and so on all the way to the top. I then placed a blue one-color shape right next to the yellow bottom shape, with the "tip" pointing "away" from the tower (leaving an empty block between the tower and the top of the blue).
After filling the left column and building my tower of alternating colors, I started making more matches at the bottom, to the right of the blue shape, while making sure that no match touched more than two others. I made no beat drops during this phase, and carefully dropped shapes so that they wouldn't create any unexpected matches. After I had 3-4 matches in the bottom by the blue shape, I finally pulled a beat drop and got 12 chains. The chain will start at the bottom right and then work its way up the tower.