The crafting feature has returned to Call of Duty, just this time, we are not playing zombies. The schematics do not need to be all built in a single game. This is cumulative. You can do it over 100+ different games if you want, and even mix and match doing them on Solo and Public.
There are 5 Schematics to be made, which are as follows:
First Area:
1) Pipe Bomb
2) Sticky Flare
Second Area entrance:
3) Hypno Trap
4) Tesla
a) Basic Tesla* - Cell Battery
b) Medium Tesla* - Liquid Battery
c) Advanced Tesla* - Nucleic Battery
Second Area Door:
5) Venom
a) Venom X** - Biolum - Green Venom (explosive / green clouds)
b) Venom FX** - Orange Biolum - Orange Venom (incendiary flames)
c) Venom LX** - Blue - Blue Venom (lightning)
d) Venom SX** - Amythyst - Purple Venom (shoots seeder turrets)
*The difference between each variation of Tesla depends on which Battery you pick up.
**The difference between each variation of Venom depends on which Biolum you pick up.
The parts can be collected from long, rectangular, red toolboxes. You need a schematic in your hand to be able to collect the items though. And if you switch a schematic while you have some items for the previous schematic, then you lose all the items.
For anyone trying to unlock this easily in solo mode:
There are always 9 in the first area (3 behind the first door, 2 behind the 2nd door and one on the pipe by the intel, and 3 in the room before the tentacle.)
There are always 6 in the second area (1 box outside the far right door, 1 inside it, 1 inside on 2nd floor, and 3 more at various locations).
I went and picked up a Tesla schematic in solo, and ran to the first door, got all the items, crafted and put it down, then ran back and got another schematic, repeat, and did it again the third time. Each time I got a different battery because it was the same game. I got rid of all 3 Tesla variations from the first area in one game quite easily.
Same for the Venom, though I did that in solo mode in area 2 and 3 (it gets tough, so no one will judge you if you quit and do the Venom variations in the first area in a 2nd game).
* I did not make this guide or video. The credit for the guide goes to the Xbox user Exalted Entity and the video creator is Amplified HD.