Custom select box?

How to make a custom select box from scratch?
I am at the point where I cant make the scroll to work so the options dont occupy too much space.

<ion-list radio-group [(ngModel)]="project">
  <ion-item *ngFor="let project of Projects">
    <ion-radio [value]="project"></ion-radio>
    <ion-label>{{project.ProjectName}}</ion-label>
  </ion-item>
</ion-list>