get slots() {
    return {
      ...super.slots,
      [this._currencyDisplayNodeSlot]: () => {
        const el = document.createElement('span');
        // The data-label attribute will make sure that FormControl adds this to
        // input[aria-labelledby]
        el.setAttribute('data-label', '');
        el.textContent = this.__currencyLabel;
        return el;
      },
    };
  }
The slot to put the currency display node in. Can be 'prefix', 'suffix', 'before' and 'after'.
Default will be 'after'.