Today (Day 4), I added other operations to the ALU math, which was AND, OR, XOR, and NOT along with the addition and subtraction circuit that I created in Day 3. Moreover, I cleaned up the circuit schematic by using tunnels and splitters rather than messy wires stretching along the canvas.
Then, I used a multiplexer to feed in the different operation (AND, OR, XOR, NOT, ADD/SUB) as inputs and used a 3-bit selector input to select the operation that was to be executed. I tested the circuit, and it worked perfectly.
Now, the only things remaining are to implement SHL and SHR for the ALU.
Lapse recording: https://lapse.hackclub.com/timelapse/qAFKFWqHWpiz