It’s a good idea to look out these two IPC training videos to learn or remind you some essentials rules on soldering :
A good drawing to master your technique :
Protect your soldering iron from oxidation and use a brass sponge rather than a Sponge Bob.
Alpes Machines advise you to solder resistors and cheap components from the top just to spare some time in the building. This is not the academic way, but it can work rather good. In that case, don’t solder both top and bottom sides. If you need to remove a component later, you just have to break it into to pieces with a cutting plier for an easier removal.
It is strongly recommended to use DIP sockets for ICs, just to swap ICs while debugging your building for example. It is also strongly advised to NOT solder the switches in a first time but test the Ctrlr some weeks and, then, finish the job. The knobs should be applied last, once everything is confirmed to work as expected because removing knobs stress the potentiometers each time more and more.
Now we can continue.