when you know a little, you might know enough... there are a few ways to build a controller. if you use a premade pcb (with al the parts on in) you only need to connect the buttons and sliders to the connectors. you can also make the electronic modules yourself (or buy the boards and connect the parts yourself) and so on. but you also have to make a suitable enclosure for your midi device, which might be a little difficult if you don't have te right tools...
but for example
THIS is an simple premade module, it allows you to connect up to 16 sliders.
you can also buy a cheap second-hand midi keyboard and rewire it to you own buttons.
a little more complicated is the midibox project. it's a hardware platform for midi devices, you can make a controller as complex as u want by adding modules. you find it
HERE