I've done that for a lot of laptops using this Win98SE floppy image: WIN98SE.zip
In the Bootable Disc tab, enable Make Image Bootable, set Emulation Type to Floppy Disk (1.44 MB), click the folder icon and choose the WIN98SE.IMG file then click OK. Now add your BIOS binary and flasher to the source list, choose ISO9660 filesystem in the Options tab and burn to a rewritable disc with Verify enabled (this is important). You may need to set your storage controller to IDE mode in the BIOS for this to work.
After the disc boots you should see the drives' letters shown by MSCDEX