How to add boot to a panel?

Question

I need to add a button to my flowLayoutPanel when clicked on the add button ( btnAdd ). My Panel is called mainPanel

NOTE : I managed to add, but I need to add the size of the other buttons.

CODE

namespace SlidingPanel
{

public partial class Form1 : Form
{

    private readonly Button[] _todosBotoes;
    public Form1()
    {

        InitializeComponent();
        //Passo 1

        _todosBotoes = mainPanel.Controls.OfType<Button>().ToArray();
    }

    private void pictureBox3_Click(object sender, EventArgs e)
    {
        this.Close();
    }

    private void bunifuImageButton1_Click(object sender, EventArgs e)
    {

        if(panel1.Width == 350)
        {    

            panel1.Visible = true;
            panel1.Width = 65;

        }

    }

    private void btnVoltar_Click(object sender, EventArgs e)
    {
        if(panel1.Width == 65)
        {

            panel1.Visible = true;
            panel1.Width = 350;


        }

    }

    private void panel1_Paint(object sender, PaintEventArgs e)
    {

        if (panel1.Width == 350)
        {
            btnVoltar.Hide();

        }
        else
        {

            btnVoltar.Show();
        }

    }



    private void txtBuscarJogo_TextChanged(object sender, EventArgs e)
    {
        //Passo 2.1
        var controles = _todosBotoes.Where(btnArcheAge => (btnArcheAge.Tag as String ?? btnArcheAge.Text).ContainsIgnoreCase(txtBuscarJogo.Text)).ToArray();
        //Passo 2.2
        mainPanel.Controls.Clear();
        //Passo 2.3
        mainPanel.Controls.AddRange(controles);
    }

    private void lblAmigos_Click(object sender, EventArgs e)
    {

    }

     private void btnAdicionar_Click(object sender, EventArgs e)
     {
         for (int i = 0; i < 1; i++)
        {
            Button button = new Button();
            button.Tag = i;


            mainPanel.Controls.Add(button);
        }
     }

}
}

namespace MyMethod
{
    public static class MyExtensions
    {
        public static bool ContainsIgnoreCase(this string source, string search)
        {
            return source.IndexOf(search, StringComparison.CurrentCultureIgnoreCase) >= 0;
        }
    }
}