You can post photos on Facebook without putting them in an album by using "Add Photos" on the web browser, "Photo" on the mobile application, or your unique post-by-email address. You can also share the photos directly from the photo application on your devices.
On the web browser, you can post photos either from "Home" page or your personal page. On the Home page, click "Add Photos/Video". On the pop-up window, choose the folder where you keep the photos. You can choose multiple photos on that folder. Click "Open". If you want to add more photos from a different folder, click the empty frame with the "+", and repeat the process. Once you have all the photos you want, click "Post" to upload all photos to your Timeline, instead of putting them into an album. On your personal page, click "Photo/Video", choose "Upload Photos/Video" instead of "Create Photo Album", and repeat steps above.
On the Facebook mobile application, click "Photo" under the search bar, in between "Status" and "Check In", and choose the photos you want from your device. You can choose multiple photos in each folder, but not from different folders like on the web browser. Once you choose the photos, you have the options to edit, add a caption or say something about each photo. You can also change the privacy viewing, for example for "public" to "friend", before posting the photos to your Timeline.
Alternatively, you can attach the photos in an email and send them to your unique post-by-email address.
On an Apple device, choose multiple photos on the Photos app, click share button at the bottom, and choose Facebook among all the options to post them on your Timeline.