app-routing.module.ts

const routes: Routes = [
{
  ...,
+  {
+    path: 'blub',
+    loadChildren: () => import('./blub/blub.module').then( m => m.BlubPageModule)
+  }
];

blub-routing.module.ts

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';

import { BlubPage } from './blub.page';

const routes: Routes = [
  {
    path: '',
    component: BlubPage
  }
];

@NgModule({
  imports: [RouterModule.forChild(routes)],
  exports: [RouterModule],
})
export class BlubPageRoutingModule {}

blub.module.ts

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule } from '@angular/forms';

import { IonicModule } from '@ionic/angular';

import { BlubPageRoutingModule } from './blub-routing.module';

import { BlubPage } from './blub.page';

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    IonicModule,
    BlubPageRoutingModule
  ],
  declarations: [BlubPage]
})
export class BlubPageModule {}

blub.page.html

<ion-header>
  <ion-toolbar>
    <ion-title>blub</ion-title>
  </ion-toolbar>
</ion-header>

<ion-content>

</ion-content>

blub.page.spec.ts

import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { IonicModule } from '@ionic/angular';

import { BlubPage } from './blub.page';

describe('BlubPage', () => {
  let component: BlubPage;
  let fixture: ComponentFixture<BlubPage>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ BlubPage ],
      imports: [IonicModule.forRoot()]
    }).compileComponents();

    fixture = TestBed.createComponent(BlubPage);
    component = fixture.componentInstance;
    fixture.detectChanges();
  }));

  it('should create', () => {
    expect(component).toBeTruthy();
  });
});

blub.page.ts

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-blub',
  templateUrl: './blub.page.html',
  styleUrls: ['./blub.page.scss'],
})
export class BlubPage implements OnInit {

  constructor() { }

  ngOnInit() {
  }

}