Insert data to a pivot table in table CreateAction?

Repeater::make('sizes')
->relationship('sizes')
->schema([
  Select::make('size_id')
  ->label('Size')
  ->options(Size::all()->pluck('size', 'id'))
  ->searchable()->preload()
  ->required()->disableOptionsWhenSelectedInSiblingRepeaterItems(),
TextInput::make('price')->suffix('$')->required()->numeric()
->inputMode('decimal'),
])->columns(2)->columnSpanFull()->minItems(1),


public function sizes(): BelongsToMany
 {
return $this->belongsToMany(Size::class, 'gem_sizes', 'gem_id', 'size_id')->withPivot('price')->withTimestamps();
  }