I copied the file single.php, which is the file used by my template to show a single post. Saved it as frontpagepost.php (in the same directory as index.php for my theme) and put this at the top of the file:
<?php /* Template Name: FrontPage */ ?>
I used the plugin "Custom Post Template" so I could easily choose the template. But I get the message that "This theme has no available custom post templates". I'm using a custom theme.