This design is based on Adafruit's orginal jig: https://learn.adafruit.com/heat-set-rig

I had some 3030 aluprofile pieces at home so at first I decided to fit the original design. Later on I have:

changed the carriage mount
dropped the lever
remodelled the upper pulley
redesigned the tool clamp to be compatible with my Hakko FX-8801 soldering tool
added a wire mount clamp on the top
BOM:

a Hakko FX-8801 soldering tool (you can use any other tool but in this case you have to remodel the inside cutout of the clamp as it was designed to be a tight fit with my Hakko FX-8801)
a piece of wood baseplate in ~250x300 mm size
1 pc M3x20 bolt for the upper pulley (no M3 nut needed)
1 pc M3x25 bolt for locking the tool clamp (no M3 nut needed)
4 pcs M3 heat-set insert for the trapezoid arm (I have used the ones from Ruthex's excellent inserts: https://www.amazon.nl/-/en/dp/B08BCRZZS3/ref=sr_1_1?dchild=1&keywords=ruthex&qid=1613643272&sr=8-1 )
2+2 pcs M3x8 Allen head bolts to mount the carriage and the tool clamp to the trapezoid arm
4 pcs M4 bolts or similar size screws to attach the bottom part to a baseplate
2+1+1 pcs M4x10 bolts for the M4 T-nuts
2+1+1 pcs M4 T-nuts to attach the bottom base, the upper cap and the limiter part to the 3030 aluprofile (the bottom / top locks are optional as the design is a tight fit)
~500 mm string for connecting the carriage to the counterweight
Feel free to alter the design: http://penoff.hu/Fusion360/heat%20set%20insert%20installation%20stand%20v44.f3d