What kind of e-bike are you trying to build? Like power, battery capacity, etc.
Other thing, not all mistakes listed in >>1952981
are exactly dangerous, just not ideal.
e.g. no insulation between balance leads and cells is not that bad if wires are heat-resistant.
I would say most grave mistakes are not putting a fuse in series with B+ or B- before BMS, not using spacers/insulation between cells and on + pole, using heatshrink as only protection material.
You can probably get away with soldering if you're fast, but manufacturers of cells advice you not to do this.
Other thing, is choice of cells. Try finding cells whose max current output is 1.25 - 1.5 times of typical current you'd draw from them. Using cells with no current margin would result in early death of cell, overheating and capacity way less than advertised.
Using cells with insanely high discharge rate might seem logical, but high discharge cells fail violent (i.e. 10A discharge cell might smoke and catch on fire, 30A discharge cell will get so hot it will shoot molten metal out of the vent).
Other thing, different chemistries are different.
LiFePO4 while has less energy density, is much safer and works well at negative temperatures.
NMC has higher energy density, but is less safe and doesn't work as nice when it is cold.
Some older chemistries, like pure cobalt oxide and manganese oxide are less safe and less dense.
Maybe it is a good idea to use LFP cells instead of NMC.
But yeah, I've no experience with LiFePO4, cuz I'm too poor to get new cells, and all my cells are re-used, and thus I don't give as much of a fuck about fire.
Or idk, maybe wait until sodium ion cells get a bit cheaper and more mass produced.