Flat ProgressBar Style

<Style TargetType="ProgressBar">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ProgressBar">
                <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}"
                        Background="{TemplateBinding Background}" CornerRadius="0" Padding="0">
                    <Grid x:Name="PART_Track">
                        <Rectangle x:Name="PART_Indicator" HorizontalAlignment="Left" Fill="{TemplateBinding Foreground}" />
                    </Grid>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>