How to use EF DbConext outside of Controller?

I'm building ASP.Net app which is a simulator, lots of action will happens outside of Controller as separate threat, but I'm struggling to create DbContext connection outside of Controller. I know I could use OnConfiguring(DbContextOptionsBuilder optionsBuilder) but it doesn't look to my as most elegant way to do it.

I through something like this should work:

public class SimRepository : ISimRepository
{
    public IConfiguration _configuration;
    public DbContextOptionsBuilder _dbOptions;

    public SimRepository(IConfiguration configuration)
    {
        _configuration = configuration;

        _dbOptions = new DbContextOptionsBuilder();
        _dbOptions.UseSqlServer(_configuration.GetConnectionString("DefaultConnection"));
    }

    public void LatheIn()
    {
        using (AppDbContext db = new AppDbContext(_dbOptions.Options))
        {

        }
    }
}

but I receive this error:

Argument 1: cannot convert from Microsoft.EntityFrameworkCore.DbContextOptions' to Microsoft.EntityFrameworkCore.DbContextOptions<Simulator_Line.Server.AppDbContext>

In Startup:

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddDbContext<AppDbContext>(options => 
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
    services.AddMvc();

    //Enable use of appsettings.json outside of Startup.cs
    services.AddSingleton(Configuration);
    services.AddSingleton<IConfiguration>(Configuration);
}

If my approach is incorrect, I'm open to for changes.

EDIT

    public class LatheController : Controller
{
    private readonly AppDbContext _dbContext;
    private readonly SimRepository _simRrepo;

    public LatheController(AppDbContext dbContext, SimRepository latheRepo)
    {
        _dbContext = dbContext;
        _simRrepo = latheRepo;
    }

    [HttpGet]
    public IEnumerable<Lathe> GetLathes()
    {
        _simRrepo.LatheIn();



        return _dbContext.Lathes;
    }
}