Send the PCB's gerber files to any PCB manufacturer (JLCPCB, PCBWay, etc.) to have the PCB made and shipped to you. Should come out to around $8 for 5 PCBs.

Need 2N7002 SOT23 (x3), 2M 0603 resistors (x2), 9.1M resistor (x1), 0603 red LED (x1), CR2032 surface mount battery clip (x1), 1N4148 SOD123 diode (x1), 47k 0603 resistor (x1), 2.2k 0603 resistor (x1), 680pF 0603 ceramic capacitor (x1), 80pF 0603 ceramic capacitor [OPTIONAL] (x1). All components should be easy to find on digikey and most from even Amazon.

Use a solder iron with a fine head to solder the components onto the PCB. Recommend using fine tweezers for soldering the 0603 components and lead free solder. Please make sure to solder in a well ventilated area or using a fume extractor! NOTE: For best reliable results it is recommended that you apply conformal coating to the top side components of the PCB (the side with the LED, transistors, etc) in order to avoid inaccurate readings that can result if these components get wet.

To "dial in" your sensor you will need to play around with how deeply the sensor is inserted into your plant's soil. If you want to have the sensor trigger earlier (ie when the soil is still somewhat slightly damp) insert the sensor only a little bit into the soil. If you'd like the sensor to only trip when the soil is very dry insert the sensor very deeply into the soil (up to the second to highest white line max)