just two 6m long 50x30x3mm (romania)
50$ worth!!!
also can make one bigger or modular - join two together
cut 1m bars, have also 1m legs and two 35cm to make the top 100x45cm
got holes 10mm at 10cm distance
got 5 tubes controlled by height for flatness @5cm distance
flatness with screws in the build is 2 per tube, but could be 4 for more control (if 2 the you might have to bend-twist it to flatness - easy because practically the skrew is bending)