In the terms of cheap, the bridgelux strips are a best bang for your buck. They’re available in 1120 mm, 560 mm, and 280 mm lengths. Basically 4 feet, 2 feet, and 1 foot. One of the major benefits of these is that you can run them at test current without heatsinks. Mounting them with to 1/8” aluminum bar with double sided thermal transfer tape will keep them well below manufacturers recommended operating temp. Makes building relatively cheap and mounting very easy.
The downside is there are kind of limited driver applications as the poke in connectors are only rated for 300 volts. And the 4’ strips have forward voltage of about 45 volts at 700 ma. Sometimes you can find a little better with 2’ strips that are 22 ish volts.