If you're on about building a machine email me on here and I'll help you however I can. That's so much easier instead of just giving you itemized steps.
Ok so a few things about my machine and about it's build and design process.
the machine (Y)1300mm (X) 850mm (Z)400mm 5mm lead on all
I am fortunate to have had access to alot of engineering equipment such as lathes, industrial milling machines and the space to build it. I would consider whether you would want to continue if you haven't got the room for a machine because the build process and the machine does take up alot of space and creates alot of dust and mess. However you could build one with basic tools and elbow grease. I used all stainless steel nuts and bolts for the fixings and the machine is built out of ITEM extrusion and c250 grade aluminum plate. which basically means machine tooling plate. So the aluminum has been machine ground flat on both surfaces.
I wasn't prepared to settle for second best either I really wanted to build something that was high quality. The machine isn't the fastest thing on the earth but it runs at full feed 800mm per min but the quality is great.
I'm not really a massive fan of the bar type rails you can purchase as they're prone to bending and movement. I've used Hiwin within my professional career and opted for them and their linear carriages because they're stupidly robust and last forever if well maintained and greased.
Same with the ball screws I opted for class 5 screws which are a more accurate grade of screw. Most home built routers I've seen are made using Class 7 screws as they're affordable and arguably there isn't much difference.. BELIEVE me there is, if you can afford to spend that little bit extra do it and don't look back.
If you're buying Chinese ball screws expect Chinese quality and the hiccups that you get along the way knew that the machine I would be building would be accurate so I took precautions and used a torque wrench when tightening things up.