Rotate the player in a certain way that makes it look like he is sliding

I'm trying to make my first game in Unity: a 3d platformer inspired by the classic Crash Bandicoot games.

I've managed to make most of the movement with the character control script below. However, I don't know how I can do a slide/crouch.

What I want to do is to rotate and move the player down closer to the ground and give him some more speed that decreases over time until he reaches a normal waking state.

I thought about making the player rotate on a specific axis but when he turns the axis doesn't change so now I'm kind of lost in what to do.

using UnityEngine;

public class PlayerMovement : MonoBehaviour
{

    public CharacterController controller;

    public float speed = 10f;

    //turnning smoothness

    public float turnSmoothTime = 0.1f;
    float turnSmoothVelocity;

    //jump controls

    public float jumpHeight = 3f;
    public float gravity = -29.43f;
    Vector3 velocity;
    bool isGrounded;

    //gravity check
    public Transform groundCheck;
    public float groundDistance = 0.4f;
    public LayerMask groundMask;

    // Update is called once per frame
    void Update()
    {
        isGrounded = Physics.CheckSphere(groundCheck.position, groundDistance, groundMask);

        if(isGrounded && velocity.y < 0)
        {
            velocity.y = -1f;
        }

       //player movement on both axis

        float horizontal = Input.GetAxisRaw("Horizontal");
        float vertical = Input.GetAxisRaw("Vertical");
        
        Vector3 direction = new Vector3(horizontal, 0f, vertical).normalized;
       
        velocity.y += gravity * Time.deltaTime;
        controller.Move(velocity * Time.deltaTime);

        if (Input.GetKeyDown("space") && isGrounded)
        {
            velocity.y += Mathf.Sqrt(jumpHeight * -2f * gravity);
        }
        
        if (direction.magnitude >= 0.1f)
        {
            //player turning depending on where moving

            float targetAngle = Mathf.Atan2(direction.x, direction.z) * Mathf.Rad2Deg;
            float angle = Mathf.SmoothDampAngle(transform.eulerAngles.y, targetAngle, ref turnSmoothVelocity, turnSmoothTime); 
            transform.rotation = Quaternion.Euler(0f, angle, 0f);
            
            controller.Move(direction * speed * Time.deltaTime);
            
        }
            
    }
}