Developing float layout into Flex Display layout - html

Question

I have been using float layout UI for my webpage. Recently i thought to convert the same layout into flex display layout. I havent been much into flex displays and i am a complete newbie into flex layout. I am struggling to convert my webpage layout into flex display. If any one could give just a gist to some properties for the UI would be helpful. I tried some with flex display but struggled with the left banner (expressed in a HTML skeleton below) as it is completely breaking the row system.
I have posted the HTML and CSS in a fiddle. Link to which is shared.
.left-block {
padding: 24px;
height: 100vh;
display: table-cell;
width: 41.66666667%;
margin: 0px;
background: #333;
/*padding: 24px 24px 0 24px;*/
}
.right-block {
padding: 24px 24px;
height: 100vh;
display: table-cell;
width: 58.33333333%;
}
.container-fluid {
max-width: 100%;
/*border-left: 1px solid #ccc;
border-right: 1px solid #ccc;*/
}
<div class="container-fluid">
<div class="row">
<div class="col-md-6 left-block">
<img src="~/images/logo.png" class="pull-left logo" />
<span class="pull-left company-name">Company Name<sup>TM</sup> </span>
<div class="clearfix"></div>
<p>
Sign in to your account.
</p>
</div>
<div class="col-md-6 right-block">
<div id="SignInBlock">
<p class="pull-right">
<span class="noacct">Don’t have an account?</span> Create account
</p>
<div class="clearfix"></div>
<div class="form-wrapper">
<h1>Sign in</h1>
<form action="#">
<div class="form-group">
<input type="email" class="form-control" id="work_email" required placeholder="Work Email">
</div>
<button type="submit" disabled class="btn btn-big btn-primary col-xs-12">Sign in</button>
</form>
<p class="forgot-password">
<strong>Forgot email?</strong>
</p>
</div>
</div>
</div>
</div>
<div class="clearfix"></div>
</div>
https://jsfiddle.net/u9wz18br/
<div class="left-block">
<!-- Full height banner with 40% width -->
// Some Text
</div>
<div class="right-block">
<!-- Create Account Link floating right -->
// Sign In Block Here
</div>