For starters, collect your tools and make an estimated arrangement, resulting in a width and height. Take those numbers with you to the hardware store and buy a flight case (or similar hard toolbox). Then grab one or two pieces of plywood, at least 10 mm thick. (mine is 18 mm, laminated)

Mount those with screws from the outside, giving nice surfaces on the inside to work with. (I used 5 for each)

Now comes the "lessons learned". I started to design custom 3D printable parts to secure the tools, without doing any research. Then, after many (literally) broken attempts, I found some PVC pipe mounting brackets. And boy, they are made for us!

These are cheap and come in several sizes - 16, 20, and 25 mm in diameter, but I bet there are different sizes in the wild. The iron tips and the soldering iron perfectly fit the 16 mm brackets. I used the 20 mm for the syringes and the suction gun, and the 25 mm one holds the hot air soldering gun. (of course, when it's cold) The brackets are mounted with a screw, just don't use too long screws!

Many other tools are attracted by magnets. I know, magnetizing tweezers can cause some mayhem, so only do this if you pack a demagnetizer! But strong magnets with mounting points are a thing, one or two screws are enough.

If you are concerned and don't want to use magnets, you can still use elastic bands or cable organizer velcro strips! Just use a strong stapler gun to mount the strips.

Last but not least, some tools have their own mounting points! My cheapo (and dangerous) soldering station has a detachable mounting flange. Use it to your advantage!

I hope I gave you some ideas for your own portable soldering solution!