Originally Posted by QuiltE

I'm like you and like random piano keys better than orderly colour/fabric switches.
Of course, for some quilts the orderly look is more appropriate.

I press at every step of the process ... with Best Press for the fabric before any cutting is done.

I've done it much like you ... and yes, slow, but yet well worth the efforts.
Here's how I do it ...
I like narrow ... so usually go for 2" or 1-1/2" strips.

For example, If I want 6" finished keys ... I cut the strips into 7-1/2" or 8" pieces.
Then I make piles of one of each fabric.
Then I sew a pile together.
I stay random, though sometimes will set a strip aside (eg. 2 of the same colour) for a different placement.
Sew pairs together, press.
Then pairs of pairs, etc. till the pile is together. Press after each seam.
Once a pile is all together ... a good final pressing and Best Pressing.
Then I trim it down to the perfect size of 6-1/2".
Gives you a nice crisp edge to work with when joining together later.

Then onwards to the next pile(s).
Join the strips from each pile together after the precision cutting!
Meanwhile, keeping in mind how many I need for a side/end ... so I don't get a group together and discover it is longer than needed.

For corners ... mitre them!

It's time consuming ... but not really difficult!
And so much FUN to see them come together.

Here's a look at one of my piano key projects .........
(sorry, I just realized I don't have a photo of this quilt after quilting was completed!)
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