It depends on whether you mean flatter or flat I suppose.
On flatter patterns, I try to play a little straighter, and pick the ball depending on volume and length, moving in and trying to increase backend later in the block.
If the oil is flat, I'll use something strong and early rolling, see how far the ball will hook. If the ball hooks, say, 9 boards, I'll play straight down 8th and just try and make good shots until the lane opens up a little, then jump in and use that area.
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Reporting from England