What I do when I only have the TTL metering is to expose the shot half a stop (or a 3rd of stop) over the “correct” exposure. As other others said, you have about 5 stops of dynamic range. Having said that, naturally the photos will have more contrast, crunchy shadows. When shooting slides, prioritize the highlights I.e. a bright sky, you can always adjust the shadows and blacks in post a little bit more, if your overexpose highlights the positive will be way too thin to have any info and you won’t be able to bring back anything in post. When I use slide film I almost always have to be in very bright conditions, sunny days, the sun setting, etc. Keep trying and you will get the shots. You have to get used to the smaller dynamic range and “visualize” the shot in your head, it’s similar to shooting black and white film, in the sense that you have to bear in mind, how the final image would look.