It is an unfortunate fact that the simpler the engine in number of moving parts, the more frighteningly complex the actual design is. While four-stroke engines may have a lot of complexity in the parts, the fact is they have a very broad range of variables under which they will still run.
In contrast, while the two-stroke, as well as some other engine designs without valves, looks very simple, the operating principles are frankly INSANE. Particularly the shape of the combustion chamber and the expansion chambers. The math involved in designing one from scratch is very, very formidable, even for a large corporation with a well-funded team. Even just designing a new exhaust system for an existing motor is a non-trivial task - everything is interconnected and the exhaust systems convergent-divergent shape serves much the same function as a camshaft as well. One of the reasons for this is that the fluid dynamics equations are all that really keeps the engine running. The pressure differentials are what are acting as valving and timing. Getting proper primary compression, moving that charge into the combustion chamber without losing it out the exhaust port or trapping too much combustion gas, getting proper combustion, and getting it to exhaust itself properly is not something I would suggest that any individual, no matter how skilled, could do from scratch.
I used to build and tune two-stroke racing engines, and even tuning and alterations to an existing design is an extremely technical science in and of itself. There is a reason two-stroke engines have lagged decades behind four-stroke development, even with people the likes of Honda having been working on R&D for decades so far.
I wish you the best, but this is not as easy as it might look just from the raw parts machining perspective. The parts are easy, calculating the exact dimensions to actually work are not!