Building a DER sequence

[Ken Goldman]

I have to build a DER byte stream for a sequence containing:
        algorithm ID
        issuer
        validity
        subject name
        extensions

What is the general approach?

Is there openssl support for this?

Do I construct a sequence and add items to it - top down?

Or do I construct the items and then make a sequence from it - bottom up?
        
Or do I place the items in a custom structure and then write the i2d() 
myself?

Any advice, pointers, or sample code would be welcome.