Project video:

Main Features (Overview):

- Incredibly smooth and stable from use of multiple linear rail blocks, a rigid frame and a T12 lead screw (as opposed to a slider with roller wheels and a belt pulley)
- Slider with opposing counterweight so that the slider can be used on a single tripod
- Feet for use without tripod
- "Manfrotto 501-style quick-release" mounting plate found on the AD-01 smallrig tripod (also ¼ inch threaded screw mounting points)
- Simple control with one potentiometer to control left and right speed. For more complex motions, the arduino nano can have custom code written.

Hardware: (JLCMC part names in italics):

2x 2020 Aluminum extrusion (1m length) TXCJ-H7-2020-L1000
4x 6301ZZ bearings (ID: 12, OD: 37, H: 12)  BCTJ-6301ZZ
~50x M3 T-slot nuts TPAA-N-6-M3
~50x Black M3*6 Hex socket machine screws EDLA-J9-M3-L6
~20x Black M3*8 Hex socket machine screws EDLA-J9-M3-L8
8x Black M3*60 Hex socket machine screws EDLA-J2-M3-L60
8x M3*25 Hex socket machine screws EDLA-J2-M3-L25
2x MGN9C Linear guide rails (0.95mm length. 3x “9C” Slider blocks per rail. Blocks may need to be purchased separately. Check total height is 10mm when measured from the bottom of the rail to the top of the block) E-BMN9C-3-L950-Z1-C-M-E15
2x 5mm to 12mm shaft coupling (Less than 37mm total diameter, less than 44mm in length.) CXKK-D36-d5-e12.7
1x Split Anodized metal box (L:120mm, 97mm 40mm height. I suggest a box wider than 97mm) K86-9740-H7-L120

2x T12 Lead screw (450mm length, 2mm lead (optional). Check nut OD is 36mm) not available on JLCMC
2x NEMA17 Stepper motor (42*42*48mm) not available on JLCMC
5x ¼ Inch heat-set insert (8mm external diameter) not available on JLCMC
8x M3 heatset insert (4mm length) not available on JLCMC

1x PCB (order attached Gerber file from JLCPCB) 
1x Arduino nano (5v operating voltage)
2x a4988 stepper motor driver (or alternative with same pinout)(or alternative with same pinout)
1x LM2596S Buck converter (set voltage to 5v before soldering)
2x 100uF electrolytic capacitor (rated for 40-50v or higher. 3.5mm wire spacing, less than 8.5mm diameter)
2x 2.54mm male pin headers (40 pins to be broken apart in to smaller strips)
6x 2.54mm 1x2 jumper connector (small jumper block to bridge to two adjacent header pins)
1x screw terminal (3.5mm pin spacing)
1x 10k potentiometer with knob
1x wire (any length - for supplying power to the main device)

Code:

#include <AccelStepper.h>

#define DRIVER_TYPE AccelStepper::DRIVER
#define STEP_PIN1 6
#define DIR_PIN1 5
#define STEP_PIN2 4
#define DIR_PIN2 3

AccelStepper stepper1(DRIVER_TYPE, STEP_PIN1, DIR_PIN1);
AccelStepper stepper2(DRIVER_TYPE, STEP_PIN2, DIR_PIN2);

const int potPin = A2;
const int deadzone = 30;
const int maxSpeed = 2500;

void setup() {
  stepper1.setMaxSpeed(maxSpeed);
  stepper2.setMaxSpeed(maxSpeed);
}

void loop() {
  int potValue = analogRead(potPin);
  int midpoint = 512;
  int delta = potValue - midpoint;

  if (abs(delta) < deadzone) {
    stepper1.setSpeed(0);
    stepper2.setSpeed(0);
  } else {
    long speed = map(abs(delta), deadzone, 512, 0, maxSpeed);
    if (delta < 0) {
      stepper1.setSpeed(-speed);
      stepper2.setSpeed(-speed);
    } else {
      stepper1.setSpeed(speed);
      stepper2.setSpeed(speed);
    } 
  }

  stepper1.runSpeed();
  stepper2.runSpeed();
}

Notes:

Thanks to JLCMC for sponsoring the project. This project is possible, easy to make, and rather affordable thanks to JLCMC's low cost custom parts. I suggest you order the hardware from JLCMC if possible. Their aluminum extrusion, nuts, screws and bearings are incredibly cheap and of high quality. Instead of ordering from sketchy unknown sellers, go to https://jlcmc.com to place your order. Refer to the video for a more in-depth explanation of JLCMC and the ordering process.

For a free $70 of coupons, check out the affiliate link below:
https://jlcmc.com/?from=MagmaBow2
If you need CNC services, JLC can also offer cheap, custom-manufactured parts at the following link:
https://jlccnc.com/?from=Magmabow

Microstepping diagram:

For any questions or support, feel free to reach out to me :)