OnChange Uncaught TypeError: Not a Function on element created by template literals from the same Class

I have an issue calling a method onChange from an element created by template literals. The element (checkbox) is created from the same class that includes a method that should be called by the onChange event. I have the following two JS files. main.js and class1.js

main.js:

import {customClass} from './customClass.js';
let customClass= new CustomClass();
customClass.createCheckBox();

customClass.js:

export class CustomClass{
     createCheckBox(){
        return `<input type="checkbox" onchange='customClass.customMethod()'`>
     }
     customMethod(){
        ...//some functionality
     }
}

When I select the checkbox I either get Uncaught TypeError: this.customMethod() is not a function or I get undefined. I tried to add this into onchange='this.customMethod() but I can’t get it working. Any help would be greatly appreciated.